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Thread: RAID configuration

  1. #1
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    RAID configuration

    what RAID configuration is good for write intensive database operation.
    J Gangadhar

  2. #2
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    0+1 : OLTP
    5 : OLAP

    So, I would say 0+1... :+)
    An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.

  3. #3
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    Yes, RAID-1 (striping if you can) and put the redo logs on physical drives with no other activity.

    (Some say RAID-5 is good for nothing http://www.dbasupport.com/forums/sho...threadid=40451 )

  4. #4
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    I agree that Raid 5 is bad in OLTP systems. My problem is I don't get a say in Hardware decisions. We're a shop that tends to use Sharks (Disk array) for the disk - both application and DB. The Shark is RAID-5 by default.

    Does anyone have any ideas on how to convince the powers-that-be that they shouldn't just use RAID-5 by default? I've grumbled about taking at least a few disks out of RAID-5 for the logs, but have been told it's not possible. When I mention the write penalty, the standard response is "The Caching takes care of that"

    Any ideas?

    We might be getting a new app in the coming months that will be OLTP, and it would be nice to get the correct hardware...

    Thanks!
    Jodie

  5. #5
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    Originally posted by jodie
    I agree that Raid 5 is bad in OLTP systems. My problem is I don't get a say in Hardware decisions. We're a shop that tends to use Sharks (Disk array) for the disk - both application and DB. The Shark is RAID-5 by default.

    Does anyone have any ideas on how to convince the powers-that-be that they shouldn't just use RAID-5 by default? I've grumbled about taking at least a few disks out of RAID-5 for the logs, but have been told it's not possible. When I mention the write penalty, the standard response is "The Caching takes care of that"

    Any ideas?

    We might be getting a new app in the coming months that will be OLTP, and it would be nice to get the correct hardware...

    Thanks!
    Jodie
    There's only three ways you can prove 0+1 is better than 5 for your application.
    1. Benchmark
    2. Benchmark
    3. Benchmark
    Jeff Hunter

  6. #6
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    I'm stmontgo and I approve of this message

  7. #7
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    Thanks for the link..

    1. Benchmark
    2. Benchmark
    3. Benchmark
    I agree, Jeff ... just can't get the disk to do it! Ugh! I'll keep trying though.

    Or, I can just wait till 10G comes out and all of this isn't necessary anymore!

    Thanks!
    Jodie

  8. #8
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    Originally posted by jodie
    When I mention the write penalty, the standard response is "The Caching takes care of that"
    How much write will the array cache?

    Also, what information is being gathered on cache overflows, if any.
    David Aldridge,
    "The Oracle Sponge"

    Senior Manager, Business Intelligence Development
    XM Satellite Radio
    Washington, DC

    Oracle ACE

  9. #9
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    Hi.

    I don't want to start a flame war, but RAID 5 is not all bad if it's used in the right way. If money were no object then I guess we would all 0+1 everything, but this is the real world and alot of companies won't.

    On some of my systems I quite happily run most of the datafiles in RAID 5 while the controlfiles, redologs etc are 0+1. It is so dependent on your hardware and requirements. We have a huge SAN with more cache than you can shake a stick at. Physical IO is actually from memory alot of the time. This makes RAID 0+1 and 5 approximately the same speed alot of the time.

    This is a note I wrote with my feelings on the matter for someone on my forum:

    http://www.oracle-base.com/articles/Misc/RAID.php

    Rules of thumb are a dangerous thing, but here are a couple:

    1) RAID 0+1 is always better than RAID 5, except when it's not.
    2) Raw filesystems are always faster than cooked ones, except when they're not.

    Last edited by TimHall; 01-26-2004 at 07:53 AM.
    Tim...
    OCP DBA 7.3, 8, 8i, 9i, 10g, 11g
    OCA PL/SQL Developer
    Oracle ACE Director
    My website: oracle-base.com
    My blog: oracle-base.com/blog

  10. #10
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    Originally posted by TimHall
    I don't want to start a flame war, but RAID 5 is not all bad if it's used in the right way. If money were no object then I guess we would all 0+1 everything, but this is the real world and alot of companies won't.
    I agree. If your box can't push enough data to saturate a RAID 5, you probably won't see any improvement with a 0+1.
    Jeff Hunter

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