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4 drive Raid 1 array on ICH9R

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March 6, 2009 8:08:48 AM

Hi,
I'm planning to set up a 4drive RAID1 array on a ICH9R onboard controller, but in the docs there are only examples of 2 disk
sets, so I wonder if it is actually possible?

More about : drive raid array ich9r

a b G Storage
March 6, 2009 10:11:08 AM

There is no logical reason to have more than 2 disks in a RAID 1 array, unless you are just over paranoid and feel you need to have 4 identical copies of your boot drive running all the time.
There are far, far, better ways to back up data.
I think maybe you are lacking somewhat in the understanding of what RAID is, what it does, and what the different types of arrays are for.
Maybe you are thinking of RAID0+1, which is two mirrored sets of drives running in RAID0?.
March 6, 2009 11:33:03 AM

I am over paranoid as i experienced 2 drives failing on a RAID 5 set on a machine where I can't afford long downtimes during the shop opening time. I have data backups and disk images on a 1TB NAS. I've studied the different RAID levels but rejected the idea of RAID 0+1 on this box as redundancy is similar
to that of a RAID 5 array and finally choose this RAID 1 with 4 drives strategy because it ensures good data protection against multiple drive failure and no need of array rebuilding with consequent performance loss. My question is rather if there is any hardware limitation on the ich9r to run a RAID 1 array with 4 drives as all documentation i was able to find always mention 2 drives only.

Ciao.
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March 7, 2009 3:28:34 AM

Well, I must say, that is a new one...no such thing as full hardware RAID 11 other than with some dual controller set-ups ( hp/compaq servers come to mind ). This will not work for an OS drive however, you can software RAID 1 2 hardware RAID 1 volumes. I've never heard of anyone doing it with RAID 1, but it is common on large scale arrays running RAID 5 ( RAID 51 ) to guard against individual controller failure. You are kinda screwed with the RAID 0+1, I agree. You could however, use this same technique to create a true RAID 10 volume ( assuming its not the OS drive ) by software striping the 2 hardware RAID 1's. While I don't exactly trust windows to handle rebuilds in the case of failures, it is definately do-able. RAID 10 will provide more fault tolerance than a RAID 5. You could handle 2 simultaneous drive failures as long as they're on seperate RAID 1 arrays and the windows software RAID 0 wouldn't even notice.

If you need to boot from one of these 4 drives, then your best bet is 2 sets of RAID 1. At least you're not putting all your eggs in 1 basket.

Kudos to you for understanding the rebuilding performance penalty, most do not.
March 7, 2009 3:58:38 AM

farmatito said:
Hi,
I'm planning to set up a 4drive RAID1 array on a ICH9R onboard controller, but in the docs there are only examples of 2 disk
sets, so I wonder if it is actually possible?


Intel raid matrix.

http://www.intel.com/support/chipsets/imsm/sb/CS-028610...

This was a simple search on Intel's website, but one that you obviously didn't do. Noobs that want to be spoon-fed are getting on my nerves.
March 7, 2009 5:28:51 AM

@croc

Quote:
Intel® Matrix Storage Manager
What two RAID volumes can I create on a single RAID array?
Matrix RAID is a feature that allows two RAID volumes to be created on a single RAID array. The following table shows the available combinations of RAID levels for each I/O controller hub.


I've read this and many more docs on the Intel site before posting and you should do the same and also read with more attention the posts
before you answer to them to avoid out of topic messages like your last one: Intel® Matrix Storage Manager allows 2 raid sets on the same
disk set.

@ ShadowFlash

Thank's, maybe I'll try two 2 Disk RAID 1 sets and backup the relevant data from one to the other during non-business time,
this would improve redundancy vs. RAID 10.
March 7, 2009 6:04:52 AM

farmatito said:
@croc

Quote:
Intel® Matrix Storage Manager
What two RAID volumes can I create on a single RAID array?
Matrix RAID is a feature that allows two RAID volumes to be created on a single RAID array. The following table shows the available combinations of RAID levels for each I/O controller hub.


I've read this and many more docs on the Intel site before posting and you should do the same and also read with more attention the posts
before you answer to them to avoid out of topic messages like your last one: Intel® Matrix Storage Manager allows 2 raid sets on the same
disk set.

@ ShadowFlash

Thank's, maybe I'll try two 2 Disk RAID 1 sets and backup the relevant data from one to the other during non-business time,
this would improve redundancy vs. RAID 10.


If you have a rev /D0, which is fairly common, then you can do raid 5, 4 or 5 drive solutions. So please re-read the documentation, verify your rev, then see what you can do. I don't care how much you have read, you obviously do not comprehend what you are reading and the implications. Not all of the ichr9r are created equal. You need to verify your data.

If you do indeed have a plain 1ch9r, early rev, then you are better off getting an aftermarket controller. Adaptec makes good ones. The better models have on-board processors for calculating the XOR algorithyms, internal non-vol flash for raid set information, etc. This means you can use a raid set on any pc...
March 7, 2009 6:49:04 AM

@croc
Quote:
I don't care how much you have read, you obviously do not comprehend what you are reading and the implications


As you said maybe I don't comprehend what i'm reading, that is the reason why I'm posting on the forum: to get some hints by some lovely person ( e.g like you), nonetheless:

1) I don't want to buy a raid controller
2) I don't want to run a Matrix raid combination
3) I don't want to be spoon fed
4) I don't want to get on your nerves

There is a simple solution to avoid it just don't answer to threads of people that "get on your nerves"

5) I wonder if with the ICH9R it is possible like with other Software raid implementations (Linux raid) to run 4 disk raid 1 arrays

If you have a better understanding of the docs a simple yes or no would suffice.

6) I'm asking if somebody tried this already so that I know it surely before buying 4 rather than 2 disks.

Ciao
a c 82 G Storage
March 7, 2009 4:47:54 PM

A 4 disk RAID 1 either is a RAID 0+1 or a RAID 1+0. Even with a hardware controller you can't setup a RAID 1 the way that you described it. If uptime is critical to your business, why didn't you have a hot spare? Did both drives fail at the same time?
March 7, 2009 5:57:33 PM

I myself run a 4 disk RAID 1 but it is implemented with linux software RAID

Personalities : [raid1] [raid6] [raid5] [raid4]
md2 : active raid1 sda1[0] sdb1[1]
244195904 blocks [2/2] [UU]
bitmap: 0/233 pages [0KB], 512KB chunk

md0 : active raid1 sdc1[0] sde1[3] sdf1[2] sdd1[1]
104320 blocks [4/4] [UUUU]
bitmap: 0/13 pages [0KB], 4KB chunk

md1 : active raid5 sdc3[0] sdd3[3](S) sde3[2] sdf3[1]
472535680 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
bitmap: 1/226 pages [4KB], 512KB chunk

Usually this is done in linux to place the boot partition on it so that you can boot your system indipendently of what drive failed if you have installed the boot loader on the MBR of each drive.

I did have a hot spare and used it to replace the first failed drive but another drive failed during the rebuild of the RAID 5 array. :_(
That's why i want to move to RAID 1.

Ciao
a c 82 G Storage
March 7, 2009 7:27:57 PM

I'm not very familiar with Linux, but I don't see evidence that 4 partitions contain identical data.
March 7, 2009 8:59:56 PM

this is our raid device: md0
it is : active
in raid1 mode
composed by sata disk sdc partition 1 which is drive number [0] of the array
composed by sata disk sde partition 1 which is drive number [3] of the array
composed by sata disk sdf partition 1 which is drive number [2] of the array
composed by sata disk sdd partition 1 which is drive number [1] of the array
the raid device counts 104320 blocks
there 4 drives out of 4 expected drives [4/4]
all of them are Up [UUUU]

;-)
a c 82 G Storage
March 7, 2009 9:18:23 PM

But how did you determine that it isn't a RAID 10? I have a lot of experience with hardware RAID solutions, but I've never seen a RAID 1 that includes 4 disks (or even 3 disks). Why 4 disks if they all contain the exact same info? Why not 3 disks?
March 7, 2009 9:46:03 PM

I set it up that way so i do know :-), however when i first experimented with it just to be sure i pulled out all the disks and having installed the boot loader on every disk the system booted the same from each of them.

In my actual box i used 4 disks as it is a multiple raid array on the same disk set and the number was due to the raid 5 set composed by 3 disks plus 1 spare drive.

| |DISK1|DISK2|DISK3 |DISK4|
---------------------------------------------------------------------------------------------------------------
| Partition 1|RAID1|RAID1|RAID1|RAID1 | (contains the kernel and an initial ramdisk to boot the system)
| Partition 2|RAID5|RAID5|RAID5|RAID5 SPARE| (contains the root file system)
| Partition 3| SWAP|SWAP|SWAP |SWAP | (non Raid, as Linux Kernel does some striping out of the box if multiple swap devices are present and set to the same priority)


Would like to do something similar on the ICH9R with winxp so that all but 1 disks of the set can fail and i still would be able to run the system during business time and replace the failed disks during non business time.

Ciao
March 8, 2009 3:50:57 PM

Yup... I did something similar with a 3 disk linux raid set up for my RAID NAS drives. RAID 1 the first partition of each (to make sure that all will boot given any one drive fails), and then RAID 5 the second partitions. Linux software raid is great for almost any setup you can think of and very easy to recover from (as long as you don't mind the cli for a few lines). I've never had a problem with it. Linux software raid is even more stable than most host RAID set ups.
March 11, 2009 4:41:41 AM

Intel's software RAID stack only supports RAID 1 with two disks.

The disk limits for the various RAID levels are as follows (some ssytems may be more restrictive):

RAID 0: 2-6 disks
RAID 1: 2 disks
RAID 5: 3-6 disks
RAID 10: 4 disks
Intel Rapid Recover Volume: 2 disks
March 14, 2009 3:35:03 PM

Yes, I experienced it empirically but while at it I decided to go for a different
strategy with 4 drives but no raid:

Drive 1: main drive in use
Drive 2: clone of drive 1, daily backup at 15.00 when shop is closed
Drive 3: clone of drive 1, daily backup at 22.00 when shop is closed
Drive 4: kept as spare and for temporary storage

So there's no need for rebuilds, no fake raid controllers throwing out good disk
for apparently no reason and in case of a bad disk i just swap them and reboot.
Of course there is a limited risk of loosing a half day's work data but this to me is more acceptable then a long downtime to reinitialize a broken raid array and restore a backup ghost image.
Thanks to all for their hints and comments.

Ciao

September 20, 2011 5:32:02 PM

Your best bet would be RAID6, 4 drives, two data, two parity drives, though the write penalty would be somewhat high, I believe it would be lower than using any sort of software raid.

Also, RAID6 provides better reduncay than anything other than true RAID11, because since RAID6 uses parity and not a combination of mirroring/striping, ANY2 drives can fail, and the array can rebuild. Also, if the controller supports it, you can expand the array at a later time by adding more drives, and expand your storage amount.

~newParadigm
September 20, 2011 5:35:22 PM

Also, I should add to my original post, that you could also add a fifth drive as a hot spare, so that the RAID controller could rebuild the array on the fly, and continue opperation. Granted there would be a performance hit while rebuilding, it would be limited because the rebuild would initiate immediately, instead of sitting there impaired until you could rpelace the drive...
!