Raid nVidia noob question :-)

[n45w73]

Noob's here ;o)

I play for the first time with my on board nVidia SataII Raid, and I got some strange numbers.

I tested my 2 HD Seagate 320g sata2 alone first
And I got using PC Wizard 2007

Sequetial writing 59.89 MB/s
Sequetial reading 70.65
Buffered writing 179.93
Buffered reading 186.26
Random reading 92
I thought I should be close to 300 MB/s ?

then I move 2 HD on my nVidia Raid on striping mode and got
Sequetial writing 74.77 MB/s
Sequetial reading 89.32
Buffered writing 173.99
Buffered reading 182.46
Random reading 103

who also suprised me, only 10 o 20 MB/s faster ...
I thought I got at least aroung 50MB/s
So is those numbers seem ok for you?

I was tempted by a raid 5,
so what should I expect from 3 hds ?
so what should I expect from 4 hds ?


Thanks


EDIT - add this benchmark ;-)

Mirroring Array with the same HDs
Sequetial writing 52.56
Sequetial reading 75.08
Buffered writing 172.21
Buffered reading 182.78
Random reading 37

 

[jt001]

Those benchmarks sound about right, and striping a second drive will not double performance, just as a dual core CPU isn't quite twice as fast. You should be getting maybe a bit better transfer rates than that when in RAID 0 though, what is your stripe size?


Any type of RAID that involves parity calculation(such as RAID 5) is a bad idea on onboard controllers. If you want to do that a dedicated RAID card is a good idea. The reason being with no XOR processor like a dedicated card usually has, it has to offload the data onto your main CPU which typically uses up about 5-10% of your cpu time. Also, it will add a lot of latency which will slow the array down a lot. If you want some numbers to play with I benchmarked 3 WD800JD drives in RAID 5 on my dedicated controller and got 12.1ms access time with 1% CPU usage, and on my onboard RAID I got 17.6ms with 8% CPU usage.

 

[mkaibear]

You should not bother with RAID 0, it's pointless, as is RAID 5 except with a dedicated controller!

(especially since the latency on a RAID 0 is worse!)

Having said that, those numbers look fine, they will increase a little with 3 or 4 drives in a RAID 0, but not an awful lot.

 

[SuperFly03]

As the previous posters said, your numbers look decent, all be it a bit on the slow side imo.

I thought I should be close to 300 MB/s ?

Yeah, right. Not insulting you, it's just that hard drives physically aren't that fast.

The 300MB/s you are talking about is theoretical potential transfer speed based on perfect efficiency on the SATA bus. In reality hard drives typically run about 45MB/s write and 50-55 MB/s read (in general, there are exceptions of course). When it comes down to it you will never utilize all that potential bandwidth on the SATA bus with a single hard drive and even if you stripe them you still can't because SATA is a point to point connection across an unshared bus, so each lane has 300MB/s of bandwidth (or 150MB/s in the case of SATA spec 1.0).

Raid 0 will never net you 100% improvement, it just doesn't scale perfectly (like all things IT related). There are inefficiencies that creep in due to overhead in order to manage the disks. In all reality, if you are a normal home user you should look at RAID 0, turn and run the exact opposite direction because there is no use for it in an average users life (there are rare instances when it is worth it). RAID 1 would be your best bet, if you want a live backup that is. RAID 5 is good because it provides more usable disk space than RAID 1 and still maintains redundancy, but requires more system resources (as a previous poster mentioned, XOR proc for parity calculations).

IMHO, Raid is the most oversold, overused, and most useless feature on motherboards these days and the only reason they include them is 1) its cheap 2) Gives them bragging rights 3) People perceive their computer to be faster with RAID when it is most likely not.

 

[supec]

have a look here:
http://www.tomshardware.com/2007/01/03/the_southbridge_battle/page13.html
seems nvidia has poor especially onboard RAID, INTEL's better...

 

[n45w73]

Hi All
Thanks for answering !

have a look here:
http://www.tomshardware.com/2007/01/03/the_southbridge_battle/page13.html
seems nvidia has poor especially onboard RAID, INTEL's better...

I didn't read it before, now I did ;-) It gave me some light on controlers ...

...The reason being with no XOR processor like a dedicated card usually has, it has to offload the data onto your main CPU ...

Yes I see it makes sense (if I remember I got around 8% CPU usage...)

...Those benchmarks sound about right ...
what is your stripe size? ...

I was using Optimal size who result into 64k, I might try 128k or lower if I can find spear time ;-)

I try a mirroring for fun with the same HDs
Sequetial writing 52.56
Sequetial reading 75.08
Buffered writing 172.21
Buffered reading 182.78
Random reading 37

...In reality hard drives typically run about 45MB/s write and 50-55 MB/s read (in general, there are exceptions of course).
When it comes down to it you will never utilize all that potential bandwidth on the SATA bus with a single hard drive and even if you stripe them you still can't because SATA is a point to point connection across an unshared bus, so each lane has 300MB/s of bandwidth (or 150MB/s in the case of SATA spec 1.0)....

I forgot to mention, but those HDs was my firsts SATA HD, so I didn't had any references before, I know I was still living into the old ATA world...
So I was a little bit surprise to see a relatively small difference between my old ATA 133 HD and my new SATA2 HD, now I see, they change the interface but the drive itself didn't really get alot faster ...

In all reality, if you are a normal home user you should look at RAID 0, turn and run the exact opposite direction because there is no use for it in an average users life (there are rare instances when it is worth it). RAID 1 would be your best bet, if you want a live backup that is. RAID 5 is good because it provides more usable disk space than RAID 1 and still maintains redundancy...

I think your right, If I can find 1 or 2 HD handy I might continue my tests on a RAID5 for fun but for my owm needs I think I will stick with one SATA2 has master storage and the other one for scheduled backup, in that way I will still be able to swap thoses HDs around my other computers without loosing data .. etc..

Or I might go for an external RAID controler one of these days.
I didn't choose my motherboard (ECS nForce 570 SLI ) for its raid capability, but for some other usefull features it offers ;-)

 

[SuperFly03]

...In reality hard drives typically run about 45MB/s write and 50-55 MB/s read (in general, there are exceptions of course).
When it comes down to it you will never utilize all that potential bandwidth on the SATA bus with a single hard drive and even if you stripe them you still can't because SATA is a point to point connection across an unshared bus, so each lane has 300MB/s of bandwidth (or 150MB/s in the case of SATA spec 1.0)....

I forgot to mention, but those HDs was my firsts SATA HD, so I didn't had any references before, I know I was still living into the old ATA world...
So I was a little bit surprise to see a relatively small difference between my old ATA 133 HD and my new SATA2 HD, now I see, they change the interface but the drive itself didn't really get alot faster ...

Yeah, I understand your confusion. It is much like PCI-e for graphics cards, it didn't really boost performance now but things will come up later on that require it. Example: SLI. The sheer bandwidth required for SLI is unfeasible on an AGP slot. SATA's day will come, but right now you really only get TCQ, NCQ, thinner cables, and a marginal boost in performance mainly related to higher areal density. Oh, and a point to point connection, not a shared bus.

In all reality, if you are a normal home user you should look at RAID 0, turn and run the exact opposite direction because there is no use for it in an average users life (there are rare instances when it is worth it). RAID 1 would be your best bet, if you want a live backup that is. RAID 5 is good because it provides more usable disk space than RAID 1 and still maintains redundancy...

I think your right, If I can find 1 or 2 HD handy I might continue my tests on a RAID5 for fun but for my owm needs I think I will stick with one SATA2 has master storage and the other one for scheduled backup, in that way I will still be able to swap thoses HDs around my other computers without loosing data .. etc..

Or I might go for an external RAID controler one of these days.
I didn't choose my motherboard (ECS nForce 570 SLI ) for its raid capability, but for some other usefull features it offers ;-)



That's how I have it setup. In my sig you'll see I have 3 hard drives, what you don't see is that the 2x 400GB are mirrored (RAID 1) and the Raptor is backed up nightly to the mirror array. So, in order for me to lose data now I would have to lose both my 400GB or 1 400GB and my Raptor. It's a nice setup

Have fun!

 

[Madwand]

For reads, there should be no problem with RAID 5 performance -- it should perform like RAID 0 with one less drive.

Stripe size of 64k / (number of data drives) can give good STR performance, because 64k requests are common (and then you break up that request among all the data drives). (Number of data drives) in RAID 5 = (number of drives in array) - 1. You need to test this though; implementations, applications, and OSs vary.

Writes are where RAID 5 implementations take their performance toll -- it can be really bad if not done correctly, e.g. 1/2 of a single drive speed.

There's some NV RAID 5 performance data in this thread:

http://forumz.tomshardware.com/hardware/fast-RAID-ftopict220943.html