topic THP Pool Volumes in XP Storage

THP Pool Volumes

Juan Carlos Mendoza Cal — Wed, 19 Aug 2009 17:32:09 GMT

I have question, i am going to implemenmtation THP on the XP24000, but what is best practices create AG 28+4 or 14+2 or 7+1 for create the Pool Volumes what is the best performance.? I see the document for ThP Xp Best Practices do not answer to this question.

Re: THP Pool Volumes

Nigel Poulton — Thu, 20 Aug 2009 13:54:59 GMT

I give the following as my personal opinion.....

Due to the random nature in which THP pages are allocated to V-VOLs I do not see concatenated Array Groups (14+2 and 28+4) being of much if any advantage over standard array groups.

Of course concatenated array groups are great for classicla thick LDEVs due to the way they lay down consecutive RAID stripes per LDEV over more spindles. However, I dont see any advantage with THP.

More important is to stick with the best practices outlined in the following paper which I wrote a while ago -

http://blogs.rupturedmonkey.com/?p=274

Nigel

Re: THP Pool Volumes

Peter Mattei — Mon, 24 Aug 2009 07:33:19 GMT

I recommend using Raid 5 (7+1) in most cases.

Exceptions:
- Only if you need very high write performance use Raid1 (2+2)
- When using SATA disks I would use Raid 6 (6+2) due to long recovery times after a disk failure

Background on using Raid5 (7+1) vs (28+4):

1. 4x (7+1) compared to 1x (28+4) has a sligtly higher overall performance
2. Having more ldevs gives you more queues and striping which is beneficial to performance

BTW: You will find a ThP whitepaper here:
http://h18006.www1.hp.com/storage/arraywhitepapers.html
Also check the ThP Manual on hp.docs > XP software

Cheers
XP-Pete

Re: THP Pool Volumes

Vincent Fleming — Mon, 24 Aug 2009 13:36:55 GMT

Peter and I are in different regions, so I thought that I would chime in here and agree with him - in the Americas we're also recommending the same as Pete outlined.

More than 95% are RAID5, 7+1. The ThP stripes over the LDEVs presented to it, so there's no advantage to 14+2 or 28+4 - in fact, the double striping seems to slow things down a little.

Good luck!