Re: Integrated perc 5/i

["Luke Lonergan" <llonergan(at)greenplum(dot)com>]

Title: Re: [PERFORM] Integrated perc 5/i

Hi Michael,

There is a problem with some Dell “perc 5” RAID cards, specifically we’ve had this problem with the 2950 as of 6 months ago – they do not support RAID10.  They have a setting that sounds like RAID10, but it actually implements spanning of mirrors.  This means that you will not get more than one disk worth of performance whether you are performing random seeks (within a one disk sized area) or sequential transfers.

I recommend you read the section in the Dell configuration guide very carefully and look for supplemental sources of technical information about it.  We found the issue clearly explained in a Dell technical memo that I don’t have in front of me – we were shocked to find this out.

As suggested – the RAID5 numbers from these controllers are very strong.

- Luke


On 8/16/07 1:26 AM, "Michael Ben-Nes" <miki(at)epoch(dot)co(dot)il> wrote:

> Hi
>
> I wanted to know if the integrated perc 5/i which come with Dell 2950 will yield maximum performance from RAID 10 ( 15K SAS ).
> Or should I ask for different card ?
>
> I read an old post that shows that RAID 10 does not work eficently under perc 5/i 
> http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&q=perc+5%2Fi+performance&rnum=6&hl=en#38837995887b6033  <http://groups.google.com/group/pgsql.performance/browse_thread/thread/b85926fe6de1f6c2/38837995887b6033?lnk=st&amp;q=perc+5%2Fi+performance&amp;rnum=6&amp;hl=en#38837995887b6033> 
>
> Does any one have any experience with RAID 10 & perc 5/i ?
>
> Thanks,
> Miki