Re: Experience with HP Smart Array P400 and SATA drives?

It could be the drives, it could be a particular interaction between them and the drivers or firmware.

Do you know if NCQ is activated for them?
Can you test a single drive JBOD through the array to the same drive through something else, perhaps the motherboard's SATA port?

You may also have better luck with software raid-0 on top of 2 4 disk raid 5's or raid 10s. But not if a single disk JBOD still performs well under par. You may need new drivers for the card, or firmware for the drive and or card. Or, the card may simply be incompatible with those drives. I've seen several hard drive - raid card incompatibilities before.

On 12/9/08 11:45 PM, "Mario Weilguni" <mweilguni(at)sime(dot)com> wrote:

Scott Marlowe schrieb:
> On Tue, Dec 9, 2008 at 5:17 AM, Mario Weilguni <mweilguni(at)sime(dot)com> wrote:
>
>> Alan Hodgson schrieb:
>>
>>>>>>> Mario Weilguni <mweilguni(at)sime(dot)com> wrote:
>>>>>>>
>>>>>>>
>>>>> strange values. An individual drive is capable of delivering 91
>>>>> MB/sec
>>>>> sequential read performance, and we get values ~102MB/sec out of a
>>>>> 8-drive RAID5, seems to be ridiculous slow.
>>>>>
>>> What command are you using to test the reads?
>>>
>>> Some recommendations to try:
>>>
>>> 1) /sbin/blockdev --setra 2048 device (where device is the partition or
>>> LVM volume)
>>>
>>> 2) Use XFS, and make sure your stripe settings match the RAID.
>>>
>>> Having said that, 102MB/sec sounds really low for any modern controller
>>> with 8 drives, regardless of tuning or filesystem choice.
>>>
>>>
>>>
>> First, thanks alot for this and all the other answers.
>>
>> I measured the raw device performance:
>> dd if=/dev/cciss/c0d0 bs=64k count=100000 of=/dev/null
>>
>> I get poor performance when all 8 drives are configured as one, large
>> RAID-5, and slightly poorer performance when configured as JBOD. In
>> production, we use XFS as FS, but I doubt this has anything to do with FS
>> tuning.
>>
>
> Yeah, having just trawled the pgsql-performance archives, there are
> plenty of instances of people having terrible performance from HP
> smart array controllers before the P800. Is it possible for you to
> trade up to a better RAID controller? Whichever salesman sold you the
> P400 should take one for the team and make this right for you.
>
>
A customer of us uses the P400 on a different machine, 8 SAS drives
(Raid 5 as well), and the performance is very, very good. So we thought
it's a good choice. Maybe the SATA drives are the root of this problem?

--
Sent via pgsql-performance mailing list (pgsql-performance(at)postgresql(dot)org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance