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RAID 0 with 3 partitions?

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Anonymous
a b G Storage
October 21, 2004 12:17:32 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Hi

I've not done RAID before so just wanted to get clear about this...

If I use RAID 0 can I then create 3 partitions within it. Or am I stuck with
one enormous partition?

If 3 partitions are possible I'm thinking separate partitions for OS, Apps,
Data.

Planning to use two WD 74Gb SATA Raptors drives so next questions is....

Would RAID 0 with 3 partitions be faster than the two separate disks set up
as Master C (OS) and D (Apps) then Slave E (Data).

Thanks for any input.

Ian

More about : raid partitions

Anonymous
a b G Storage
October 22, 2004 2:49:52 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Ian Roberts <sorry@nospam.com> wrote:
> Hi

> I've not done RAID before so just wanted to get clear about this...

> If I use RAID 0 can I then create 3 partitions within it. Or am I
> stuck with one enormous partition?

Ordinarily RAID creates one larger "logical" disk from smaller ones.
You should be able to treat it just like a regular disk. Depending
on the controller/software used, you might get less than this.

Most/all hardwware-RAID solutions should give you this view. Linux
software RAID does.

> If 3 partitions are possible I'm thinking separate partitions for
> OS, Apps, Data.

> Planning to use two WD 74Gb SATA Raptors drives so next questions is....

> Would RAID 0 with 3 partitions be faster than the two separate disks
> set up as Master C (OS) and D (Apps) then Slave E (Data).

Depends. The only good figures I have are from Linux software RAID:
About same speed on writes (maybe a bit slower). About 180%
speed of the individual disks on mostly linear reads, up to the
practical PCI-bus limit (i.e. RAID0 with 4 disks will not be 4 times
faster today than with 2-3 disks).

For shorter or non-linear reads/writes, the answer is that it depends.
If you really need high speed, you need to investigate. If on the other
hand you are find with having everything on a single Raptor,
depending on the RAID controller/software used, RAID0 should be not
much slower that a single disk and might be significantly fater
for some access patterns.

However using a cheap RAID controller or a mediocre software
solution can slow down things considerably.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus
Anonymous
a b G Storage
October 22, 2004 3:28:47 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

You can partition a RAID 0 array. I have 3 partitions on mine (two NTFS, one
FAT32). This was set up with the XP utilities, although I used Partiton
Magic 8 to format the FAT32 partition, as it's larger than 32 GB. (XP
supports FAT32 partitions larger than 32 GB, it just won't format them.) I
guess that hardware RAID arrays look like single drives to the disk
utilities, including the DOS-based ones I've tried (Partition Magic, Ghost),
even though the utilities may not be certified to work with RAID systems.

The rest of your questions I can't answer. I've read a few online articles
lately ( http://www.anandtech.com/storage/showdoc.aspx?i=2101) that claim
that SATA RAID 0 is largely wasted. I suspect that what holds for gamers and
users of office applications may not apply to video editing. (As I don't do
video editing, it's just speculation.)

Address scrambled. Replace nkbob with bobkn.

"Ian Roberts" <sorry@NOSPAM.com> wrote in message
news:cl7npa$sph$1@ngspool-d02.news.aol.com...
> Hi
>
> I've not done RAID before so just wanted to get clear about this...
>
> If I use RAID 0 can I then create 3 partitions within it. Or am I stuck
> with one enormous partition?
>
> If 3 partitions are possible I'm thinking separate partitions for OS,
> Apps, Data.
>
> Planning to use two WD 74Gb SATA Raptors drives so next questions is....
>
> Would RAID 0 with 3 partitions be faster than the two separate disks set
> up as Master C (OS) and D (Apps) then Slave E (Data).
>
> Thanks for any input.
>
> Ian
>
>
>
>
Related resources
Anonymous
a b G Storage
October 23, 2004 4:59:19 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
> Previously Ian Roberts <sorry@nospam.com> wrote:
> > Hi
>
> > I've not done RAID before so just wanted to get clear about this...
>
> > If I use RAID 0 can I then create 3 partitions within it. Or am I
> > stuck with one enormous partition?
>
> Ordinarily RAID creates one larger

> "logical" disk from smaller ones.

Nonsense.
'Striping' disk drives simulates a larger 'physical' disk to the operating system.
So does 'JBOD'.
'Mirroring' does not.

'"logical" disks' are partitions.

> You should be able to treat it just like a regular disk. Depending
> on the controller/software used, you might get less than this.

Less than what?

>
> Most/all hardwware-RAID solutions should give you this view. Linux
> software RAID does.
>
> > If 3 partitions are possible I'm thinking separate partitions for
> > OS, Apps, Data.
>
> > Planning to use two WD 74Gb SATA Raptors drives so next questions is....
>
> > Would RAID 0 with 3 partitions be faster than the two separate disks
> > set up as Master C (OS) and D (Apps) then Slave E (Data).
>
> Depends. The only good figures I have are from Linux software RAID:
> About same speed on writes (maybe a bit slower). About 180%
> speed of the individual disks on mostly linear reads, up to the
> practical PCI-bus limit (i.e. RAID0 with 4 disks will not be 4 times
> faster today than with 2-3 disks).

On desktop MoBos and add-on SATA controllers.
MoBos with that many channels on the MoBo Chipset or server/
professional workstation MoBos don't have that restriction.

>
> For shorter or non-linear reads/writes, the answer is that it depends.
> If you really need high speed, you need to investigate. If on the other
> hand you are find with having everything on a single Raptor,
> depending on the RAID controller/software used,

> RAID0 should be not much slower that a single disk and
> might be significantly fater for some access patterns.

So what it comes down to is that when your access pattern is mainly
random access small file the RAID0 isn't going to help.
In that case seperating OS Apps and DATA onto different physical
drives cuts down on the headmovements per drive and with SATA even
allows concurrent access at all time, provided that the OS supports it.

>
> However using a cheap RAID controller or a mediocre software
> solution can slow down things considerably.
>
> Arno
Anonymous
a b G Storage
October 23, 2004 7:54:04 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
> "Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
>> Previously Ian Roberts <sorry@nospam.com> wrote:
>> > Hi
>>
>> > I've not done RAID before so just wanted to get clear about this...
>>
>> > If I use RAID 0 can I then create 3 partitions within it. Or am I
>> > stuck with one enormous partition?
>>
>> Ordinarily RAID creates one larger

>> "logical" disk from smaller ones.

> Nonsense.
> 'Striping' disk drives simulates a larger 'physical' disk to the operating system.
> So does 'JBOD'.
> 'Mirroring' does not.

> '"logical" disks' are partitions.

There is no unified terminology. On Linux this is a block device.
On Windows I have no idea.

On the other hand on BSD a "partition" is called a "slice".

The term ''logical'' can however be used in its original meaning,
namely a thing simulating to be something else while being composed
from smaller parts or being part of a larger thing. That is the
reason I used the quotes.

[...]
>> Depends. The only good figures I have are from Linux software RAID:
>> About same speed on writes (maybe a bit slower). About 180%
>> speed of the individual disks on mostly linear reads, up to the
>> practical PCI-bus limit (i.e. RAID0 with 4 disks will not be 4 times
>> faster today than with 2-3 disks).

> On desktop MoBos and add-on SATA controllers.
> MoBos with that many channels on the MoBo Chipset or server/
> professional workstation MoBos don't have that restriction.

Yes, and since that is the standard case my answer is for it.
Of couse, if you use, e.g., a PCI-X controller you can get more
even with add-on cards. But all these are special cases and
have to be looked at individually, since all these solutions
have their own limits. You will not get 500MB/sec reading from
an 8-way RAID5, even though the disks may be able to do that
unless you have pretty unusual hardware.

As an exapmple I get 90MB/sec sustained linear reads from an
8 way software-RAID with two Promise 150TX4 controllers in
a 66MHZ PCI bus on a "professional" dual CPU board. One nice
thing is that this rate does _not_ level off at the end
of the disks were they are slower since they are still much
faster than the bus.

There is also the problem that many mainboards do not have
all (S)ATA channels in the chipset but some of them logically
connected to the PCI bus. Of course you will get better rates
if the controllers are on some faster internal bus.

All in all the answer to the speed question is that it
depends very much on the set-up. Server mainboards are
not necessarily faster. They are usually more reliable and
more expensive.

>> For shorter or non-linear reads/writes, the answer is that it depends.
>> If you really need high speed, you need to investigate. If on the other
>> hand you are find with having everything on a single Raptor,
>> depending on the RAID controller/software used,

>> RAID0 should be not much slower that a single disk and
>> might be significantly fater for some access patterns.

> So what it comes down to is that when your access pattern is mainly
> random access small file the RAID0 isn't going to help.

Yes. Or at least it depends very much on the disk-sheduling used.
I have no figures on this.

> In that case seperating OS Apps and DATA onto different physical
> drives cuts down on the headmovements per drive and with SATA even
> allows concurrent access at all time, provided that the OS supports it.

Yes, definitely. Although the improved reliability of RAID0 may be
more important. To me it is.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus
Anonymous
a b G Storage
October 23, 2004 9:05:18 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Arno Wagner <me@privacy.net> wrote:
> Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
>> "Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
>>> Previously Ian Roberts <sorry@nospam.com> wrote:
>>> > Hi
>>>
>>> > I've not done RAID before so just wanted to get clear about this...
>>>
>>> > If I use RAID 0 can I then create 3 partitions within it. Or am I
>>> > stuck with one enormous partition?
>>>
>>> Ordinarily RAID creates one larger

>>> "logical" disk from smaller ones.

>> Nonsense.
>> 'Striping' disk drives simulates a larger 'physical' disk to the operating system.
>> So does 'JBOD'.
>> 'Mirroring' does not.

>> '"logical" disks' are partitions.

> There is no unified terminology. On Linux this is a block device.
> On Windows I have no idea.

> On the other hand on BSD a "partition" is called a "slice".

> The term ''logical'' can however be used in its original meaning,
> namely a thing simulating to be something else while being composed
> from smaller parts or being part of a larger thing. That is the
> reason I used the quotes.

[...]
> Yes, definitely. Although the improved reliability of RAID0 may be
> more important. To me it is.

Oops, sorry about that. Momentary confusion with RAID1. Actually
RAID0 is far less reliable than a single drive. If yo have drives
to spare I would advise to go to RAID1. As fast as RAID0 on reads
but a lot more reliable.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus
Anonymous
a b G Storage
October 23, 2004 9:26:02 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Hello,

I have here 2 WD 40 GB drives in RAID0 and an extra drive that holds the
system. The RAID0 array is split into 3 partitions (d:, f: and g:) ,
while the extra system drive is split in 2 partitions (c: and e:) .

I have Windows 98 SE, so no special software buffering and the RAID0 is
on a cheap RAID controller card.

The c: and e: partitions (containing the system and some archives) are
acting slow (the more fragmetned the worse), something like 64 kbps
(partition to partition) to 128 kbps (partition to network or memory),
while the RAID0 partitions (d:, f: and g: containing all program files,
the swap file [makes software load and CDs burn FAST], all personal
files and all junk files) are very fast, if they are defragmented or not
makes no diffirence, around 96 kbps (partition to partition) to 256 kbps
(partition to network or memory).

Now while I likely converted the units wrong, the RAID0 I have on two
drives is around 4 times faster than the plain disk one.

And yes, it's quite easy to have as many partitions as you want on a
RAID array. Each RAID array acts exactly like one disk to the OS (just
faster/whatever of course).

Ian Roberts wrote:
> I've not done RAID before so just wanted to get clear about this...
>
> If I use RAID 0 can I then create 3 partitions within it. Or am I stuck with
> one enormous partition?
>
> If 3 partitions are possible I'm thinking separate partitions for OS, Apps,
> Data.
>
> Planning to use two WD 74Gb SATA Raptors drives so next questions is....
>
> Would RAID 0 with 3 partitions be faster than the two separate disks set up
> as Master C (OS) and D (Apps) then Slave E (Data).
>
> Thanks for any input.


--
Primary function: Coprocessor
Secondary function: Cluster commander
Anonymous
a b G Storage
October 23, 2004 10:04:17 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Folkert Rienstra wrote:
> So what it comes down to is that when your access pattern is mainly
> random access small file the RAID0 isn't going to help.
> In that case seperating OS Apps and DATA onto different physical
> drives cuts down on the headmovements per drive and with SATA even
> allows concurrent access at all time, provided that the OS supports it.

Nonsense. You read bechmarks too much.

1. Moving drives from the main controller to a RAID card can boost
things like CD writing anyhow.

2. Operating systems without large disk caches can make use of the
convenient disk buffer usualy present on a RAID controller.

3. Most software is composed of blocks that load off the disk in one
chunk. With a defined RAID0 strip width of about 1 kb, and a
non-prehistorc OS, files too small to benerfit from the speed gained
with RAID0 simply do not exist.

4. Systems utilizing anything that can relate to the Windows swap file,
gain awesomely in preformance, because the swap file is usualy a 700+ MB
block. In windows, when resizing of this file occurs, it's being read
and rewritten in one go, the speed of this imporves greately with RAID0.
Even on systems where swap file resizing never occurs, synchronization
between the memory and the swap file is preformed in one go likewise and
the preformance gain is rather great.

5. Many home users can also greately benerfit from RAID0, as movies and
other digital multimedia mostly represents very big files, which can
thus be opened and copied around much faster.

6. Any system that utilizes Direct Memory Access for disk access
(practicaly ANY non-prehistoric system), does not actually preform as
many seeks, but randomly reads/writes to the memory then synchronizes
the memory with the harddrive, again in one go, utilizing a RAID0
configuration even more (only true in hardware RAID implementations).

It is greately decieving to claim that RAID0 is not actually usefull to
anyone who does not deal with large files often (heck, most home users
don't even know they're actually dealing with huge huge files when they
copy around digital movies). Sure I can understand it's recomeneded to
people who really render huge huge files onto their harddrives every 2
minutes, but... With the fact that most home users could have great
preformance, simply by plugging their harddrives elsewhere or flipping a
switch in BIOS, claiming there is no preformance boost is simply not ok.


--
Primary function: Coprocessor
Secondary function: Cluster commander
Anonymous
a b G Storage
October 26, 2004 4:39:31 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Arno Wagner" <me@privacy.net> wrote in message news:2tu2usF23sjqlU1@uni-berlin.de
> Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
> > "Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
> > > Previously Ian Roberts <sorry@nospam.com> wrote:
> > > > Hi
> > >
> > > > I've not done RAID before so just wanted to get clear about this...
> > >
> > > > If I use RAID 0 can I then create 3 partitions within it. Or am I
> > > > stuck with one enormous partition?
> > >
> > > Ordinarily RAID creates one larger
>
> > > "logical" disk from smaller ones.
>
> > Nonsense.
> > 'Striping' disk drives simulates a larger 'physical' disk to the operating system.
> > So does 'JBOD'.
> > 'Mirroring' does not.
>
> > '"logical" disks' are partitions.
>
> There is no unified terminology. On Linux this is a block device.
> On Windows I have no idea.
>
> On the other hand on BSD a "partition" is called a "slice".
>
> The term ''logical'' can however be used in its original meaning,
> namely a thing simulating to be something else while being composed
> from smaller parts or being part of a larger thing. That is the
> reason I used the quotes.
>
> [...]
> > > Depends. The only good figures I have are from Linux software RAID:
> > > About same speed on writes (maybe a bit slower). About 180%
> > > speed of the individual disks on mostly linear reads, up to the
> > > practical PCI-bus limit (i.e. RAID0 with 4 disks will not be 4 times
> > > faster today than with 2-3 disks).
>
> > On desktop MoBos and add-on SATA controllers.
> > MoBos with that many channels on the MoBo Chipset or server/
> > professional workstation MoBos don't have that restriction.
>
> Yes, and since that is the standard case my answer is for it.

Which you failed to make clear.

> Of couse, if you use, e.g., a PCI-X controller you can get more
> even with add-on cards. But all these are special cases and
> have to be looked at individually, since all these solutions
> have their own limits. You will not get 500MB/sec reading from
> an 8-way RAID5, even though the disks may be able to do that
> unless you have pretty unusual hardware.

Having 8 drives in RAID-5 on a desktop is what I would call unusual.

>
> As an exapmple I get 90MB/sec sustained linear reads from an
> 8 way software-RAID with two Promise 150TX4 controllers in
> a 66MHZ PCI bus on a "professional" dual CPU board.

Sounds awful to me. You must be doing something wrong.

> One nice thing is that this

awful

> rate does _not_ level off at the end of the disks were they are
> slower since they are still much faster than the bus.

90MB/s is way below the capacity of that bus.

>
> There is also the problem that many mainboards do not have
> all (S)ATA channels in the chipset but some of them logically
> connected to the PCI bus. Of course you will get better rates
> if the controllers are on some faster internal bus.

Like Fast/Wide (66MHz/64-bit) PCI or PCI-X or PCI-Express.

>
> All in all the answer to the speed question is that it
> depends very much on the set-up.

> Server mainboards are not necessarily faster.

Yes they are, although faster in server type usage may be character-
ized more like "less slow" than with running on a desktop system.

> They are usually more reliable

Just another chipset from the same mfgr of MoBo chipsets.
PCI64/66 used to be an addon chip to a standard MoBo chipset.

> and more expensive.
>
> > > For shorter or non-linear reads/writes, the answer is that it depends.
> > > If you really need high speed, you need to investigate. If on the other
> > > hand you are find with having everything on a single Raptor,
> > > depending on the RAID controller/software used,
>
> > > RAID0 should be not much slower that a single disk and
> > > might be significantly fater for some access patterns.
>
> > So what it comes down to is that when your access pattern is mainly
> > random access small file the RAID0 isn't going to help.
>
> Yes. Or at least it depends very much on the disk-sheduling used.
> I have no figures on this.
>
> > In that case seperating OS Apps and DATA onto different physical
> > drives cuts down on the headmovements per drive and with SATA even
> > allows concurrent access at all time, provided that the OS supports it.
>
> Yes, definitely. Although the improved reliability of RAID0 may be
> more important. To me it is.
>
> Arno
Anonymous
a b G Storage
October 26, 2004 4:45:01 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Arno Wagner" <me@privacy.net> wrote in message news:2tvhaeF23t557U1@uni-berlin.de
> Previously Arno Wagner <me@privacy.net> wrote:
> > Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
> > > "Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
> > > > Previously Ian Roberts <sorry@nospam.com> wrote:
> > > > > Hi
> > > >
> > > > > I've not done RAID before so just wanted to get clear about this...
> > > >
> > > > > If I use RAID 0 can I then create 3 partitions within it. Or am I
> > > > > stuck with one enormous partition?
> > > >
> > > > Ordinarily RAID creates one larger
>
> > > > "logical" disk from smaller ones.
>
> > > Nonsense.
> > > 'Striping' disk drives simulates a larger 'physical' disk to the operating system.
> > > So does 'JBOD'.
> > > 'Mirroring' does not.
>
> > > '"logical" disks' are partitions.
>
> > There is no unified terminology. On Linux this is a block device.
> > On Windows I have no idea.
>
> > On the other hand on BSD a "partition" is called a "slice".
>
> > The term ''logical'' can however be used in its original meaning,

It is misleading when such term is already being used by e.g. Fdisk and
-because of that- probably by any other partitioning type software.

> > namely a thing simulating to be something else while being composed
> > from smaller parts or being part of a larger thing. That is the
> > reason I used the quotes.
>
> [...]
> > Yes, definitely. Although the improved reliability of RAID0 may be
> > more important. To me it is.
>
> Oops, sorry about that. Momentary confusion with RAID1. Actually
> RAID0 is far less reliable than a single drive. If yo have drives
> to spare I would advise to go to RAID1.

> As fast as RAID0 on reads

Only for accesses that are multiple IOs and a RAID1 imple-
mentation that spreads such multiple IO evenly over the drives.

> but a lot more reliable.

>
> Arno
Anonymous
a b G Storage
October 27, 2004 8:42:22 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

On Tue, 26 Oct 2004 00:45:01 +0200, "Folkert Rienstra"
<see_reply-to@myweb.nl> wrote:

>"Arno Wagner" <me@privacy.net> wrote in message news:2tvhaeF23t557U1@uni-berlin.de
>> Previously Arno Wagner <me@privacy.net> wrote:
>> > Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
>> > > "Arno Wagner" <me@privacy.net> wrote in message news:2tqsogF22un5iU2@uni-berlin.de
>> > > > Previously Ian Roberts <sorry@nospam.com> wrote:
>> > > > > Hi
>> > > >
>> > > > > I've not done RAID before so just wanted to get clear about this...
>> > > >
>> > > > > If I use RAID 0 can I then create 3 partitions within it. Or am I
>> > > > > stuck with one enormous partition?
>> > > >
>> > > > Ordinarily RAID creates one larger
>>
>> > > > "logical" disk from smaller ones.
>>
>> > > Nonsense.
>> > > 'Striping' disk drives simulates a larger 'physical' disk to the operating system.
Right. this is called a logical disk

>> > > So does 'JBOD'.
>> > > 'Mirroring' does not.
>>
>> > > '"logical" disks' are partitions.
no. Partitions are paritions. partitions hold logical volumes.

>> > There is no unified terminology. On Linux this is a block device.
>> > On Windows I have no idea.
>>
>> > On the other hand on BSD a "partition" is called a "slice".
>>
>> > The term ''logical'' can however be used in its original meaning,
>
>It is misleading when such term is already being used by e.g. Fdisk and
>-because of that- probably by any other partitioning type software.

You should not be so easily misled. 'logical disk' is a standard term
used by raid manufacturers. Raid manuals both use and explain this
term.
Anonymous
a b G Storage
November 8, 2004 4:12:57 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Bob Knowlden wrote:

> The rest of your questions I can't answer. I've read a few online articles
> lately ( http://www.anandtech.com/storage/showdoc.aspx?i=2101) that claim
> that SATA RAID 0 is largely wasted. I suspect that what holds for gamers and
> users of office applications may not apply to video editing. (As I don't do
> video editing, it's just speculation.)

That article is mostly rubbish.

Try any benchmark, shows no diffirence between RAID0 and normal disks,
but try booting from it, copying movies around it or transfering over
LAN from it and suddenly RAID0 beats normal disks by a factor of 4.

I've tried a bechmark program on my computer, it decided my RAID0 array
was slower than that stand-alone disk I boot from, while it's perfectly
evident that a program loads from the stand-alone disk in 10 seconds
while from the RAID0 array in less than two (Paint Shop Pro 7).

My point: Bechmarks are bullshit, try it yourself.

The other thing perfectly true is that RAID0 can get you accross much
cheaper than stand-alone disks.

1. RAID0 is the cheapest way to get a home user 500 Gigs of disk space
in one piece.

2. You don't have to buy very expensive drives to get peak preformance
from them and the controller card is plain cheap (if RAID0 isn't already
supported by your motherboard).

3. You never ever have to defragment a RAID0 array, preformance does not
degrade with file fragmentation as with stand-alone drives and the disk
contens take much more time to fragment as much as in stand-alone drives.

4. RAID0 is an old and well-tested technology and does not cause
dissaster with CD-ROMs and uncompatible harddrives as for example the
Prefetch technology or any other weird preformance boosters available in
mobos.

--
Primary function: Coprocessor
Secondary function: Cluster commander

"We are Pentium. Accuracy is irrelevant. You will be approximated."
Anonymous
a b G Storage
November 8, 2004 4:12:58 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Jure Sah <jure.sah@guest.arnes.si> wrote:
> Bob Knowlden wrote:

>> The rest of your questions I can't answer. I've read a few online articles
>> lately ( http://www.anandtech.com/storage/showdoc.aspx?i=2101) that claim
>> that SATA RAID 0 is largely wasted. I suspect that what holds for gamers and
>> users of office applications may not apply to video editing. (As I don't do
>> video editing, it's just speculation.)

> That article is mostly rubbish.

> Try any benchmark, shows no diffirence between RAID0 and normal disks,
> but try booting from it, copying movies around it or transfering over
> LAN from it and suddenly RAID0 beats normal disks by a factor of 4.

> I've tried a bechmark program on my computer, it decided my RAID0 array
> was slower than that stand-alone disk I boot from, while it's perfectly
> evident that a program loads from the stand-alone disk in 10 seconds
> while from the RAID0 array in less than two (Paint Shop Pro 7).

That speed-up seems rather unlikely, unless the I/O sheduling of
the OS is really, really broken. Was this perhaps a situation
were the fast start was not the first from that disk and parts
still in the cache memory of the OS?

> My point: Bechmarks are bullshit, try it yourself.

Benchmarks are specific. Ni general-purpose benchmarks exist or can
exist, since access patterns are vastly different for different uses
and disk-layouts (and fragmentation state).

> The other thing perfectly true is that RAID0 can get you accross much
> cheaper than stand-alone disks.

Huh? And why is that?

> 1. RAID0 is the cheapest way to get a home user 500 Gigs of disk space
> in one piece.

Why do you want it in one piece? Are you a fan of fragmentation,
losses due to large clusers and catastrophic single partition
failures?

> 2. You don't have to buy very expensive drives to get peak preformance
> from them and the controller card is plain cheap (if RAID0 isn't already
> supported by your motherboard).

Or OS. Still peak performance is what you get at the price
of negative peake reliability. It is not called RAID-ZERO
for no reason.

> 3. You never ever have to defragment a RAID0 array, preformance does not
> degrade with file fragmentation as with stand-alone drives and the disk
> contens take much more time to fragment as much as in stand-alone drives.

This is nonsense. A RAID0 degrades just like other arrangements
when fragmented. It also fragments just as much as any other
arrangement of the same size, since the part of the OS that
does fragmentation does not know the difference.

> 4. RAID0 is an old and well-tested technology and does not cause
> dissaster with CD-ROMs and uncompatible harddrives as for example the
> Prefetch technology or any other weird preformance boosters available in
> mobos.

Well, yes. If you are willing to live with very low reliability
and the very real possibility to loose the whole array. If it is
just unimportant stuff or ar disk-based buffer, RAID0 has some merits.
However even calling it 'storage' may be overoptimistic.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus
Anonymous
a b G Storage
November 8, 2004 6:44:55 PM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

On 8 Nov 2004 12:42:12 GMT, Arno Wagner <me@privacy.net> wrote:


>> 4. RAID0 is an old and well-tested technology and does not cause
>> dissaster with CD-ROMs and uncompatible harddrives as for example the
>> Prefetch technology or any other weird preformance boosters available in
>> mobos.
>
>Well, yes. If you are willing to live with very low reliability
>and the very real possibility to loose the whole array. If it is
>just unimportant stuff or ar disk-based buffer, RAID0 has some merits.
>However even calling it 'storage' may be overoptimistic.
>
>Arno

Indeed. I agree with your points Arno. I think this is the most
important one. MTBF of an array is equal to the MTBF of an individual
drive divided by the number of drives in the array. When 1 disk has
problems so does the entire striped set.

As far as performance I wonder if some of the performance limitations
are related to lack of spindle synchronization (rotational position
locking). Rather than explaining here see:
http://www.uni-mainz.de/~neuffer/scsi/what_is_raid.html
under "2. Data Striping" 3rd paragraph

Hard disk manufacturers argue that spindle synchronization is no
longer necessary due to faster spindle speeds and more intelligent
firmware. I wonder if it just due to the lack of popularity of levels
like 3 and the can of worms RPL tends to open up (I think there are
licensing & acceptance issues with IBM's master-independent solution).
Anonymous
a b G Storage
November 9, 2004 4:03:11 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Curious George" <CG@email.net> wrote in message news:r13vo0tnia0gvjn060un9lh52e7eriuhoo@4ax.com
> On 8 Nov 2004 12:42:12 GMT, Arno Wagner <me@privacy.net> wrote:
>
> > > 4. RAID0 is an old and well-tested technology and does not cause
> > > dissaster with CD-ROMs and uncompatible harddrives as for example the
> > > Prefetch technology or any other weird preformance boosters available in
> > > mobos.
> >
> > Well, yes. If you are willing to live with very low reliability
> > and the very real possibility to loose the whole array. If it is
> > just unimportant stuff or ar disk-based buffer, RAID0 has some merits.
> > However even calling it 'storage' may be overoptimistic.
> >
> > Arno
>
> Indeed.

> I agree with your points Arno.

You like living dangerously?

> I think this is the most important one. MTBF of an array is equal to the
> MTBF of an individual drive divided by the number of drives in the array.

But that still says nothing about when or if your drives will die.

> When 1 disk has problems so does the entire striped set.

So it doesn't make it better than a single drive, but not worse either.

>
> As far as performance I wonder if some of the performance
> limitations are related to lack of spindle synchronization
> (rotational position locking). Rather than explaining here see:
> http://www.uni-mainz.de/~neuffer/scsi/what_is_raid.html
> under "2. Data Striping" 3rd paragraph
>
> Hard disk manufacturers argue that spindle synchronization is no
> longer necessary due to faster spindle speeds and

> more intelligent firmware.

Like maybe that drives reorder reading/writing blocks within a command
so that no revs are lost when the first block position in the command was
just missed on the media and the drive just reads/writes from the position
that it is at and reads/writes the 'lost' blocks at the end of the command.

Or that the Raid firmware just handles drives on a come first basis instead
of in a fixed order.

> I wonder if it just due to the lack of popularity of levels like 3 and
> the can of worms RPL tends to open up (I think there are licensing
> & acceptance issues with IBM's master-independent solution).
Anonymous
a b G Storage
November 9, 2004 4:04:16 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Wotanidiot.

"Jure Sah" <jure.sah@guest.arnes.si> wrote in message news:qoJjd.5342$F6.1280217@news.siol.net
> Bob Knowlden wrote:
>
> > The rest of your questions I can't answer. I've read a few online articles
> > lately ( http://www.anandtech.com/storage/showdoc.aspx?i=2101) that claim
> > that SATA RAID 0 is largely wasted. I suspect that what holds for gamers and
> > users of office applications may not apply to video editing. (As I don't do
> > video editing, it's just speculation.)
>
> That article is mostly rubbish.
>
> Try any benchmark, shows no diffirence between RAID0 and normal disks,
> but try booting from it, copying movies around it or transfering over
> LAN from it and suddenly RAID0 beats normal disks by a factor of 4.
>
> I've tried a bechmark program on my computer, it decided my RAID0 array
> was slower than that stand-alone disk I boot from, while it's perfectly
> evident that a program loads from the stand-alone disk in 10 seconds
> while from the RAID0 array in less than two (Paint Shop Pro 7).
>
> My point: Bechmarks are bullshit, try it yourself.
>
> The other thing perfectly true is that RAID0 can get you accross much
> cheaper than stand-alone disks.
>
> 1. RAID0 is the cheapest way to get a home user 500 Gigs of disk space
> in one piece.
>
> 2. You don't have to buy very expensive drives to get peak preformance
> from them and the controller card is plain cheap (if RAID0 isn't already
> supported by your motherboard).
>
> 3. You never ever have to defragment a RAID0 array, preformance does not
> degrade with file fragmentation as with stand-alone drives and the disk
> contens take much more time to fragment as much as in stand-alone drives.
>
> 4. RAID0 is an old and well-tested technology and does not cause
> dissaster with CD-ROMs and uncompatible harddrives as for example the
> Prefetch technology or any other weird preformance boosters available in
> mobos.
Anonymous
a b G Storage
November 9, 2004 7:20:47 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
> "Curious George" <CG@email.net> wrote in message news:r13vo0tnia0gvjn060un9lh52e7eriuhoo@4ax.com
>> On 8 Nov 2004 12:42:12 GMT, Arno Wagner <me@privacy.net> wrote:
[...]
>> I think this is the most important one. MTBF of an array is equal to the
>> MTBF of an individual drive divided by the number of drives in the array.

> But that still says nothing about when or if your drives will die.

>> When 1 disk has problems so does the entire striped set.

> So it doesn't make it better than a single drive, but not worse either.

Quite to the contrary. In RAID0 the MTBF for data loss is the
reliability of the overall array. You still have one working disk
if one of a pair breaks, but _all_ data is lost, effectively halving
the MTBF. The thing is that in RAID0 the data on one disk also breaks
if the other disk fails.

With two independent disks, you have the same probability of experiencing
data loss as result of a disk failure as in a RAID0 of two disks,
however you will only loose half the data in a one-disk failure.

If you normalize this on capacity, RAID0 with a pair of disks has
half the reliability per bit than a pair ofindependent disks.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus
Anonymous
a b G Storage
November 9, 2004 9:37:35 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Folkert Rienstra wrote:
>

> > I think this is the most important one. MTBF of an array is equal to the
> > MTBF of an individual drive divided by the number of drives in the array.
>
> But that still says nothing about when or if your drives will die.
>
> > When 1 disk has problems so does the entire striped set.
>
> So it doesn't make it better than a single drive, but not worse either.


Come on, Folkert - how can you say a single drive is as susceptible to
failure as RAID 0 with 2 drives?

You been at the spirits again?


Odie
--

RetroData
Data Recovery Experts
www.retrodata.co.uk
Anonymous
a b G Storage
November 9, 2004 10:25:07 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

On Tue, 9 Nov 2004 01:03:11 +0100, "Folkert Rienstra"
<see_reply-to@myweb.nl> wrote:

>> I think this is the most important one. MTBF of an array is equal to the
>> MTBF of an individual drive divided by the number of drives in the array.
>
>But that still says nothing about when or if your drives will die.

True but that's because there isn't a nice way of
characterizing/predicting that. MTBF, with all it's flaws is a
standard statistical relibility term. How exactly would you describe
the statistical reliability of drive arrays?

>> When 1 disk has problems so does the entire striped set.
>
>So it doesn't make it better than a single drive, but not worse either.

How do you come to that?
Anonymous
a b G Storage
November 10, 2004 1:29:56 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Curious George" <CG@email.net> wrote in message news:rmr0p0d7itkh8ii02sj6nj5a63upsjifli@4ax.com
> On Tue, 9 Nov 2004 01:03:11 +0100, "Folkert Rienstra" <see_reply-to@myweb.nl> wrote:
>
> > > I think this is the most important one. MTBF of an array is equal to the
> > > MTBF of an individual drive divided by the number of drives in the array.

Come to think of it, I believe that that is false.
It is only true if the added drive is one of the failing population and that is only
a few percent of the total population of drives. So if you add a drive that isn't
in the failing group the MTBF is still the same.

> >
> > But that still says nothing about when or if your drives will die.
>
> True but that's because there isn't a nice way of characterizing/predicting that.

> MTBF, with all it's flaws is a standard statistical reliability term.

But doesn't describe "your" drive. It describes the mean time between failure
for the whole population of drives (but only the ones expected to fail). Unless you
own the whole population or a significant part of the population you can't say any-
thing about whether you will be hit and if so *when* you will be hit with a failure.
MTBF describes the mean time between one drive failure and the next, averaged,
if you know how to break it down.

> How exactly would you describe the statistical reliability of drive arrays?

Rather crude:
With a single drive that is going to die at moment x there are two possibilities
when adding another one to form an array: there is a 50% chance that that
drive dies sooner and a 50% chance that it dies later than the first one.
Yet the chance that the array will have died at moment x is still 100%.

But you can't say that the second drive makes the array less reliable because
you might have used that drive as a single drive as well and not have complained.

I don't rate the chance of being 'lucky' as a rate of reliability.

>
> > > When 1 disk has problems so does the entire striped set.
> >
> > So it doesn't make it better than a single drive, but not worse either.
>
> How do you come to that?

Because when the single drive dies, it too is dead. Dead is dead, period.
Anonymous
a b G Storage
November 10, 2004 1:31:20 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Arno Wagner" <me@privacy.net> wrote in message news:2vausvF2j3lknU1@uni-berlin.de
> Previously Folkert Rienstra <see_reply-to@myweb.nl> wrote:
> > "Curious George" <CG@email.net> wrote in message news:r13vo0tnia0gvjn060un9lh52e7eriuhoo@4ax.com
> > > On 8 Nov 2004 12:42:12 GMT, Arno Wagner <me@privacy.net> wrote:
> [...]
> > > I think this is the most important one. MTBF of an array is equal to the
> > > MTBF of an individual drive divided by the number of drives in the array.
>
> > But that still says nothing about when or if your drives will die.
>
> > > When 1 disk has problems so does the entire striped set.
>
> > So it doesn't make it better than a single drive, but not worse either.
>
> Quite to the contrary. In RAID0 the

> MTBF for data loss

MTBF for dataloss?

> is the reliability of the overall array. You still have one working disk
> if one of a pair breaks,

> but _all_ data is lost,

'Lost' is relative. Half your data is lost, the other half may be
worthless. Some may be salvaged. Try that with a single dead drive.

> effectively halving the MTBF. The thing is that in RAID0
> the data on one disk also breaks if the other disk fails.
>
> With two independent disks,

Who said anything about "two independent disks"?

> you have the same probability of experiencing
> data loss as result of a disk failure as in a RAID0 of two disks,

Thanks for debunking your earlier statement that Raid0 shouldn't
even be considered storage.

> however you will only loose half the data in a one-disk failure.

Right, but that wasn't the context of my comment.

>
> If you normalize this on capacity, RAID0 with a pair of disks has
> half the reliability per bit than a pair of independent disks.

You can't compare MTBF with reliability.
MTBF describes the failing drives of the total drive population
(i.e. 100% unreliability).

>
> Arno
Anonymous
a b G Storage
November 10, 2004 7:42:52 AM

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

On Tue, 9 Nov 2004 22:29:56 +0100, "Folkert Rienstra"
<see_reply-to@myweb.nl> wrote:

>"Curious George" <CG@email.net> wrote in message news:rmr0p0d7itkh8ii02sj6nj5a63upsjifli@4ax.com
>> On Tue, 9 Nov 2004 01:03:11 +0100, "Folkert Rienstra" <see_reply-to@myweb.nl> wrote:
>>
>> > > I think this is the most important one. MTBF of an array is equal to the
>> > > MTBF of an individual drive divided by the number of drives in the array.
>
>Come to think of it, I believe that that is false.
>It is only true if the added drive is one of the failing population and that is only
>a few percent of the total population of drives. So if you add a drive that isn't
>in the failing group the MTBF is still the same.

That doesn't really make any sense. MTBF doesn't seek to describe
individual drives and the percentile of failing drives is going to
change over time - so you can't approach it that way. Furthermore
adding drives adds complexity to the disk subsystem and increased
chances of infant mortality, premature death, etc. as well as a single
failing drive (whether of mature years or not) messing up the data on
other healthy drives. Maybe MTBF is not an ideal way of describing
this, but if it is totally wrong a whole lot of people need to be
reeducated as the prevailing way of describing array reliability is
array MTBF= drive MTBF/n drives in array.

Sure if you add a drive from a "failing group" it will die prematurely
& if you have all good drives they will last past their estimated
service life and probably go around the same time. But the whole
point of descriptive tools like MTBF is to account for a
_whole_population_ (whether it does this well or not).

>> > But that still says nothing about when or if your drives will die.
>>
>> True but that's because there isn't a nice way of characterizing/predicting that.
>
>> MTBF, with all it's flaws is a standard statistical reliability term.
>
>But doesn't describe "your" drive. It describes the mean time between failure
>for the whole population of drives (but only the ones expected to fail).

We're not talking about "my drive." We are talking about the chances
of suffering problems with an array of drives as compared to a single
drive. When you put drives together in an array a more complex animal
is created.

> Unless you
>own the whole population or a significant part of the population you can't say any-
>thing about whether you will be hit and if so *when* you will be hit with a failure.
>MTBF describes the mean time between one drive failure and the next, averaged,
>if you know how to break it down.

MTBF is an extrapolated largely theoretical number so it never
accurately correlates to real world use of the whole population.
Disclosed MTBF is generally _theoretical_MTBF so it provides a
guesstimate based on a theoretical model of reality. It is something
to be taken with a grain of salt anyway. _Operational_MTBF is
generally not disclosed by manufacturers as it tends to be different
than the number they used to sell the product. MTBF is an
extrapolation based on the aggregate analysis of large numbers of
drives over (generally) a short period of time & says nothing about a
particular disk.

>> How exactly would you describe the statistical reliability of drive arrays?
>
>Rather crude:
>With a single drive that is going to die at moment x there are two possibilities
>when adding another one to form an array: there is a 50% chance that that
>drive dies sooner and a 50% chance that it dies later than the first one.

>Yet the chance that the array will have died at moment x is still 100%.

Rather crude indeed. So the array is always dead? You messed that up
pretty bad.

Array reliability doesn't correlate to flipping a two sided coin on
the first day of "statistics" as covered in grade school math. You're
missing that the point is to characterize the shift in extrapolated
up-time/reliability NOT whether an array or individual disk is up at a
particular time. Characterizing drive health in a binary way: either
it is up or it is dead is just restating the obvious and explains
nothing useful.

>But you can't say that the second drive makes the array less reliable because
>you might have used that drive as a single drive as well and not have complained.

Sure I would have complained, it's just a question of when. Nothing
lasts forever. And just because it may not suffer an infant death
doesn't mean it has a 100% chance of running 100% reliably for the
full estimated service life.

More importantly, when you use them together the array goes down as
soon as the first one to fail does so. Therefore up-time RAID0 =
actual life of shortest living drive of the array- but you can't
accurately predict actual lifespan so we are forced to deal with more
complex and somewhat problematic statistical
explanations/extrapolations.

>I don't rate the chance of being 'lucky' as a rate of reliability.

Rather convoluted.
You are indeed counting on being lucky, that is to say you expect to
not have a mixture of good and sub par/subtly damaged drives in an
array and that either drives work 100% correctly or they are offline.
The real world doesn't operate that way.

Your problem with the prevailing MTBF calculation of an array is "But
that still says nothing about when or if your drives will die" and
your explanation centers around a binary view of health at "moment x"
(without limitation). These are incompatible insofar as one does not
explain the other. A point in time is different than a time
frame/length of time.

>> > > When 1 disk has problems so does the entire striped set.
>> >
>> > So it doesn't make it better than a single drive, but not worse either.
>>
>> How do you come to that?
>
>Because when the single drive dies, it too is dead. Dead is dead, period.

Not true. It's just not the case that either a drive works 100%
accurately or it is completely dead. That happens sometimes but what
is far more likely is a period where a drive is failing and errors are
creeping in before it has to be removed. This is unacceptable in any
environment and difficult to combat without intelligent use of
redundant data/drives. When no redundant data is available individual
drives are preferred because it is easier to contain/limit such
problems. In raid0, because the drives depend on each other, the
reliability of the good drives in the array is limited by the first
one to fail/begin to fail. Because that is hard to predict for many
reasons you can neither say something like array service life is
halved with a 2 drive raid 0 nor say expected reliability is identical
because I always have a 50% chance that any particular drive I choose
will work.

Your idea that adding drives to an array does not affect reliability &
up-time of a disk subsystem is completely unique - and it is that way
for a reason. To assert that a more complex system has the same
likelihood for something to go wrong as a much simpler one makes no
intuitive or practical sense. It's curious that while you despise
newbs and are eager to slam them many of your arguments such as this
one tend to pander to them, as no one who knows any better would
believe you. I've been giving you the benefit of the doubt, so far,
but come on- enough trolling, Folkert.
!