SQL Server Performance

Disable Disk Cache

Discussion in 'Performance Tuning for Hardware Configurations' started by neo302, May 19, 2006.

  1. neo302 New Member

    Hey,

    How do you disable disk caching in Windows?
    When looking at the policy on the RAID controller,
    it has the caching selected, but both selections
    are grayed out and I can't change them.

    In the bios PERC RAID setup we have the cache
    set to write thru instead of write back.

    We want to see if this will help with the slow
    SQL 2005 inserted.

    Thanks!
  2. joechang New Member

    the OS driver should already have write cache disabled for all disks on the RAID controller,
    if the controller has battery backup, it might be ok to enable write cache
  3. neo302 New Member

    quote:Originally posted by joechang

    the OS driver should already have write cache disabled for all disks on the RAID controller,
    if the controller has battery backup, it might be ok to enable write cache

    Hey Joe,
    I was wondering b/c our 2005 Sql continues to drop info over time that is in memory.
    Thanks for the info!
    J
  4. joechang New Member

    i would be stunned to find that SQL loses info
    which Dell PERC do you have?
    for the Dell model number, look in the system and read the chips on the controller
    or look at the driver name

    if its LSI or megaraid, ok, if its adaptec, throw the adapter away quickly

    spell out in detail why you think SQL is losing rows/updates
    use Lumigent to look through the logs
  5. neo302 New Member

    quote:Originally posted by joechang
    [use Lumigent to look through the logs

    Hey Joe,

    We have the Dell Perc 4E/Di. We have 3 Raid 0 containers.
    RAID A=36g * 2 15K
    RAID B=146g * 2 15K
    RAID C=146g * 2 15K

    We call most of the time well over 100 SPs a second. 99% Inserting. Not sure
    if you remember from previous posts, but the SQL 2000 box which is slower handles
    it. Sql 2005 drops info. I disabled hyperthreading and that helped.
    We modded the cache settings in the BIOS on the cards yesterday and it
    did terrible today.

    Thanks!
    Justin
  6. derrickleggett New Member

    What cache settings did you modify? What did you modify them to? What does your physical read and write queue lengths look like on each of these LUNs? Do you have another controller card you can drop into the server just to verify it's not causing an issue?

    Out of curiousity, are you getting deadlocks on this server? That could make it seem to be "losing" information.

    Also, is this the imbedded controller? I know some Dell servers come with an imbedded 4E/Di controller. I can't remember which ones though. Are you getting any errors in SQL Server, the array software, or the event logs?

    MeanOldDBA
    derrickleggett@hotmail.com

    When life gives you a lemon, fire the DBA.

Share This Page