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P400 performance

 
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Pierguido
Advisor

P400 performance

Hi.
I've a pretty new ML350 G5 with a P400 raid card with 256 BBWC and an array of four disks in raid5.
I'm not expecting too much from this controller, but i'd like to know what are the performance normally you should get with configuration.
I'm running linux with the latest kernel and ext3 as main filesystem.
Now with a sequential write i get almost 90mb/s (according to dd).
Is there some ways to tune this card?
Thanks

Pier
11 REPLIES
Shiraj Fernando
Regular Advisor

Re: P400 performance

Hi,

Have you tried tuning with the Array Configuration Utility ? U can tune the Array Accelerator using ACU.

Hope you have installed Proliant Support Pack after the OS installation.

If not you can download the latest PSP and install it.

What distro are u running ?

Regards,
Shiraj.

MStoumba
Frequent Advisor

Re: P400 performance

What cluster size do you set when you built the array?
Pierguido
Advisor

Re: P400 performance

I'm using Debian Etch with the latest stable kernel on this server and acu (CLI) is installed...but what can i tune?
I tried differente stripe sizes and as far as i know i cannot manage the write/read cache performance.
As i see from acu, ncq is enabled.
On the OS side, i tried many things...the fs is alligned with the stripe size and i'm using lvm on it. I tried many tuning with different io schedeler and other small tunings.
All the result don't differ too much...all are between 85-90 MB/s. Is this the limit of this controller? A similar configuration with 3ware i get more than double performance and with areca i get even more.
Thanks for the help.

Pier
Pierguido
Advisor

Re: P400 performance

Sorry, i forgot to say that stripe size right now is 64k (i think is the default) and the volume is 1,5 Tbyte (4 500GB disk).

Pier
Patrick Terlisten
Honored Contributor

Re: P400 performance

Hello Pier,

what type of disks do you use?

RAID 5 suffers under a phenomenon called "write penalty". The write penalty is the overhead which arises if a block is written. A logical write is divided into two logical reads and two logical write. So while doing a write IO you can only get 25% of the possible IOPS. If you're using 15k disks, each disk achieves approx 200 IOPS. So your four disks can do up to 800 IOPS while doing 100% read. Doing a write IO you can get only 200 IOPS. That is only that, what a disk can physically do. According to that a short formula:

MB/s = IOPS x transfer size

Doing 4 KB IOPS you can get only round about 800 KB/s while doing a write IO on that four disk RAID 5.

That's all theory. The RAID is supported by cache, a intelligent controller... etc.

What I'm trying to say:

Cache and a fast controller is one thing. The right RAID Level for the right application is the other thing. Doing heavy write I/Os with a RAID 5 is... mmmhh... unwise. ;)

90 MB/s with a four disks RAID 5 is quite good. If you want more performance, try RAID 1+0. But remember: RAID 5 usable capacity = n disks -1. RAID 1+0 = n disks /2. You get the same usable capacity, you need 6 disks, not 4.

Hope this helps.

Best regards,
Patrick
Best regards,
Patrick
Pierguido
Advisor

Re: P400 performance

Hi Patrick.
Well...that was a nice explanation...i've read about that write penalty about raid5 writing.
But i was not suspecting that was so bad...i mean i always worked with some bigger raid 5 arrays (14-16 disks) and the performance were (actually still are) pretty good.
Now i know that if i want performance i can go with raid 1+0.
The last question: adding one more disk is worthing in gain of performance or it's better to keep it as spare disk (as i thought to do at the beginning)?
Thank everybody for the help.

Pier
juan quesada
Respected Contributor

Re: P400 performance

Hi,

to add a little bit more of info start reading from page 77

http://bizsupport.austin.hp.com/bc/docs/support/SupportManual/c00729544/c00729544.pdf
Patrick Terlisten
Honored Contributor
Solution

Re: P400 performance

Hello Pier,

simple answer: More disks = more IOPS. But for the same rate of write IOPS in a RAID 5 you need much more disks then in a RAID 1.

Two links that are maybe interesting for you (sorry, only in german):

http://www.blazilla.de/index.php?/archives/270-MBs-vs.-IOPS.html
http://www.blazilla.de/index.php?/archives/269-IOPS-Kalkulation.html

Don't forget to assign points. ;)

Hope this helps.

Best regards,
Patrick
Best regards,
Patrick
Pierguido
Advisor

Re: P400 performance

Thanks everybody.
Those links were very helpful.
For german no problem, ich kann noch ein bisschen deutsch verstehen ;-) (i hope i wrote it right :-))

Pier
Pierguido
Advisor

Re: P400 performance

One question more: do you have some sites, links or resources where i can go a bit deeper about storage?
Thanks

Pier
Patrick Terlisten
Honored Contributor

Re: P400 performance

Hello Pier,

one good link is www.hp.com. ;) Take a look at the support corner of the EVA. There you will find the SAN Design Reference Guide. Here is the direct link: http://bizsupport.austin.hp.com/bc/docs/support/SupportManual/c00403562/c00403562.pdf

There are some nice blogs about storage, for example http://storageadvisors.adaptec.com.

Search amazon.com for some books. There are some nice books on the market. A nice german one is " Speichernetze. Grundlagen und Einsatz von Fibre Channel SAN, NAS, iSCSI und InfiniBand

Speichernetze. Grundlagen und Einsatz von Fibre Channel SAN, NAS, iSCSI und InfiniBand von Ulf Troppens, Rainer Erkens, und Wolfgang Müller". Some english books:

"Using SANs and NAS. Help for Storage Administrators" written by W. Curtis Preston

"Designing Storage Area Networks: A Practical Reference for Implementing Fibre Channel and IP SANs" by Tom Clark

Best regards,
Patrick
Best regards,
Patrick