topic Re: optimal raid size in Disk Enclosures

optimal raid size

Burba Viktor — Thu, 18 Mar 2010 14:14:37 GMT

Hi guys,

I have a question, regarding RAID5 performance. Basically I have ProLiant Server with P400 controller with attached MSA70 shelf on it. MSA70 has 12 SATA 500GB 7.2K HDDs. The question is what is the best way to organize 12 x 500GB SATA HDDs in RAID groups. I know it is always trade off between performance and available space. But would you recommend to build RAID5 over 12 HDDs? Is there any HP recommendations on how to choose RAID group size?

Thank you in advance,
Viktor

Re: optimal raid size

Víctor Cespón — Thu, 18 Mar 2010 14:50:42 GMT

10 - 12 disks is usually considered the safe limit for RAID 5. Beyond that, use 2 RAID 5 or one RAID 6.

Re: optimal raid size

Jason Cobb — Thu, 18 Mar 2010 15:23:58 GMT

I have not tried the 500GB SATA drives in the MSA70 with a P400, but on an older shelf (MSA20)/ controller (6404) we saw very slow (+1 day on a busy array) rebuild times with 12 drives in a R5 setup. You may want to test reconstruct times with your config, or consider using R6 or at least designating an online spare. It really depends on how comfortable you are with exposure during a raid rebuild operation, and how important the data is for your situation.

Re: optimal raid size

Rob Leadbeater — Thu, 18 Mar 2010 16:01:36 GMT

Hi Viktor,

If you do go for 10-12 drives in a RAID-5 array then you run the risk of more than one drive failing at the same time, which is more likely if the drives are from the same manufacturing batch.

Personally, I'd go with RAID-6 or create 2 x RAID-5 arrays with 6 drives each.

Cheers,

Rob

Re: optimal raid size

Burba Viktor — Fri, 19 Mar 2010 09:33:14 GMT

Thank you guys for advice