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  • Latest Post - ‏2014-02-10T16:04:01Z by AndersLorensen
16 Posts

Pinned topic V7000 RAID Architecture

‏2014-02-05T22:15:30Z | v7000

We're deploying a few new V7000 systems (previously using Gen2 XIV).  All SAS 900GB 10K drives plus some SSD for EasyTier.

Vendor / IBM has advised that we should be using RAID5 RAID groups (mdisks in V7000/SVC nomenclature I guess).  Sounds like there are some solid reasons for doing this, but there's some internal hesitation around these larger drives and whether or not we should be using RAID6 instead.

Some of the reasons we've been given to accept any risks that go along with RAID5 are that we're using relatively small RAID groups, rebuild times on the V7000 are very quick (<1hr?) due to the RAID group size and other optimizations in the Storwize stack, and that disks are "pre-failed".

Any thoughts/feedback from the field?  Obviously we'd for sure go RAID6 if we were using NL-SAS....

  • AndersLorensen
    157 Posts

    Re: V7000 RAID Architecture


    Storwize, like most other storage systems do read SMART data from the disks, and can predict when a disk is about to fail.

    You would normally make MDISKs with 7-9 disks. So its not that big a set of data that needs to be rebuilded. Default behaviour is Raid5 for SAS disks and Raid6 for NL-SAS disks. But you can manually change this if you like it differently.

    If your SAS drives are going to be very heavy loaded most of the time, slowing down a rebuild, I'd consider going with Raid6, otherwise I'd not hessitate going with Raid5. Of course you should have enough hot spares as well.

    Rebuild times depends on amount of data on the disk. With 900 GB 10k Drives in our V3700 a rebuild took around 4 hours last time we lost a disk in a Raid5 (7+1) The MDISK was about 75% full of data. But the load on that system is really low. (2000 IOPS at Peaks, and most of that is served from 4 400GB SSD's)

    So dont expect 1 hour rebuilds, but expect less than 6-ish hours.