Optimal RAID configuration for DAS

  • We are planning to deploy a new server with 2x146GB 10K 6Gbps SAS HDD internal and DAS with

    12x146GB 15K 6Gb SAS HDD for hosting several databases with 70/30 read/write ratio.

    What would be the optimal RAID configuration? I was thinking of:

    (2 disk) RAID 1 internal OS + SQL Binaries

    (2 disk) RAID 1 Tran logs

    (2 disk) RAID 1 TempDB

    (2 disk) RAID 1 Backups

    (6 disk) RAID 10 or RAID 5 ? Data files

    Or maybe:

    (2 disk) RAID 1 internal OS + SQL Binaries + Backups

    (2 disk) RAID 1 Tran logs

    (2 disk) RAID 1 TempDB

    (8 disk) RAID 10 or RAID 5 ? Data files

    This server also acts as a mirror in database mirroring. What would be the best volume to place the mirrored

    database files?

    Thanks

  • Is the DAS purchased or ou can still have other options like a SAN?

    If not, what's the budget?

  • DAS is already purchased

  • Ok, stepping aside, not my strongest expertise.

  • Either of those would do. I'd prefer the first one and RAID 10 over RAID 5 if space isn't an issue. The read/write ratio is handy, but do you have any idea of the number of IOPS as this is the major limiting factor.

    I'd be a bit concerned that you have only allowed 146GB for backups but have a lot more space for data: 438GB (at 6 x RAID 10) up to 1022GB (at 8 x RAID 5). Even with compression you may have a space issue with backups, unless you know your databases are smaller. If the databases are smaller why som much disk?

    The options to think about are:

    5 X RAID 5 for data (584GB usefull)

    3 X RAID 5 for Backups (292GB Usefull)

    I know you will take a write hit, but it may give you the space you need for backups.

    Mirroring isn't my area, but I'd probably put the mirror databases files with the other databases as long as the disks can manage the IOPS.

    Cheers

    Leo

    Leo
    Nothing in life is ever so complicated that with a little work it can't be made more complicated.

  • Thanks for your reply, Leo.

    Total size for the database files is 70 GB, therefore space for backups is not an issue.

    I'm going to check the number of IOPS on existing production server tomorrow.

  • vlad s (8/2/2011)


    Thanks for your reply, Leo.

    Total size for the database files is 70 GB, therefore space for backups is not an issue.

    I'm going to check the number of IOPS on existing production server tomorrow.

    Ya but 10 days of backups + logs is ± 1TB if you don't compress. This adds up really fast.

    That not counting growth, test db (or restore)...

  • This is an IOPS statistics for the data files volume from the existing production server:

    Avg Disk Writes/sec 160

    Avg Disk Reads/sec 240

    And we do use backup compression with RedGate.

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