Raw devices
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Thread: Raw devices

  1. #1
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    DBAs,

    I'm sure that this is also one of those discussed-to-death topics but still...

    Are there any situations where Raw File Systems are the first (and may be the only) choice for database files ? Is the database size one of the criterion for deciding @ this ? If yes, can a close to a terrabyte size db be a compelling reason to go for RFS and OPS ?

    What can be the other considerations here ? I keep on hearing that the DBA job becomes more difficult in RFS. Is this true ? If yes, in what sense ?

    Does anyone have some kind of performance comparison figures between dbs on RFS and conventional (they call it Cooked) file systems ?

    Any info on this topic please...Thanks
    svk

  2. #2
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    may be you can have a look at Note 37914.1 and 23037.1 on Metalink

    [Edited by pando on 11-19-2001 at 05:39 PM]

  3. #3
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    Are there any situations where Raw File Systems are the first (and may be the only) choice for database files ?
    Yes, for example with Oracle Parallel Server (Real Application Cluster) you must use raw devices for most files. It is actually only the archivelogs which are cooked.

    Is the database size one of the criterion for deciding @ this ?
    No.

    What can be the other considerations here ? I keep on hearing that the DBA job becomes more difficult in RFS. Is this true ? If yes, in what sense ?
    No really. I use raw partitions. Once you create them, things go back to normal (What's normal :-))

    The major problem you might face is estimating the maximum for the partititions.



  4. #4
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    Talking

    Hello

    Please refer Oracle 24X7 tips and techniques by venkat devraj there is a excellent treatise on the subject for a discussion on raw file systems vs cooked file ssytems.

    beware that raw file systems are difficult to manage because you cannot run normal os commands on them.(as there is no file systems)

    With tools like Logical volume manager and the performance improvements in filesystems if you are not using OPS i am against raw file systems

    regards
    Hrishy

  5. #5
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    With tools like Logical volume manager and the performance improvements in filesystems if you are not using OPS i am against raw file systems
    Absolutely right. If you don't need them, forget about them.

    There is a myth + debate about online logs being on raw devices. You will see DBAs who will explain you why it is so important that the redologs should be on raw partitions, there are the DBA who say that it really doesn't matter noawdays.

    If you are really interested on the subject read "Why raw log files" at http://www.ixora.com.au/tips/creation/raw_log_files.htm

    or even better read "Why Raw Datafiles"

    http://www.ixora.com.au/tips/creation/raw_datafiles.htm


  6. #6
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    Jul 2000
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    Thanks folks. Its informative.
    svk

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