SQL Server Performance

Raid 0 vs Raid 1for transaction logs

Discussion in 'Performance Tuning for Hardware Configurations' started by countcet, Oct 11, 2006.

  1. countcet New Member

    I am about to take on a project where we are adding two new drives to our server. The server was not originally configured by us and we are questioning the performance.

    Currently we have a mirror for our OS
    We have 6 drives that are configured for RAID 5 (15k rpm)which has our data and 2 disk RAID 1 (10k rpm) that contains the logs.

    We are going to remove the two slower drives from the RAID 1 and replace them with 4 smaller 15k drives which will be a RAID 5.

    Is this the right thing to do? I would prefer a RAID 0 for Transaction Logs but if we lose a disk, SQL would stop functioning.

  2. Argyle New Member

    I would set the 4 drives as RAID0+1 to improve write performance and not RAID5.
  3. bradmcgehee New Member

    RAID 0 is always a poor choice for logs. About the only reason you might use RAID 0 is if you dedicated an array to the tempdb, but even then, I am not sure it would be a good choice.

    RAID 5, as Argyle has mentioned, is not a great choice for a dedicated log array as RAID 5 has a lot of overhead. RAID 1 or 10 is a better choice.

    Brad M. McGehee, SQL Server MVP
  4. joechang New Member

    i think you should do proper analysis first
    2 10K disks in RAID 1 is just fine for logs except for log backups, which disrupts the sequential access pattern
  5. countcet New Member

    I think there is a need to reclaim the two larger 10k drives.

    I would do a RAID 0+1 but these drives are only 36GB drives so I would have a MAX drive space of 72GB. I would hope that that could host the logs alone but I am not sure.

  6. joechang New Member

    if your logs are 72GB, then you need to rethink what you are trying to do
  7. countcet New Member

    They aren't that Large. Probably closer to 15 GB total for both instances.

    I am now proposing the purchase four 72 GB drives for RAID 0+1.

  8. satya Moderator

    15GB for Transaction log is not a big size as I can see in my experience, but you need to consider whether that much space will be used by the application or any other process. Periodically it is better to shrink (not regularly) and asses the performance during the jobs.

    Satya SKJ
    Microsoft SQL Server MVP
    Contributing Editor & Forums Moderator
    This posting is provided AS IS with no rights for the sake of knowledge sharing.

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