RE: Configuring Oracle with RAID and OFA

>Hi all,
>
>I am configuring a system for use with Oracle and
>am confused on the concepts
>of RAID and OFA, specifically how they work
>together.
>
>I inherited a system that is a RAID 5 utilizing 5
>disks. Oracle8i (8.1.7) is
>currently running on it. The database is setup on
>one disk (data files,
>control files, redo logs, etc.).
>
>I understand that striping spreads the info out
>across all the disks. That
>being true, is it necessary to put the redo logs,
>rollback segments, etc on
>sepaparte disks ala OFA?
>
>Since the database is not in production yet, I have
>time to make these changes
>(not to mention we are planning to redo the setup
>with Red Hat Advanced
>Server and upgrade to Oracle9i).
>
>Thanks in advance for your help. Feel free to
>point me to additional reading
>materials that will clarify this for me.
>
>Dwayne

Dwayne,

   First I have rarely heard people enthusing about Oracle on RAID 5 ...    Standards are here more for clarity than performance. Carefully laying out your files used to have some meaning, when you knew that you had a number of separate controllers and different disks, and that this controller was managing this disk, and by assigning this file to this disk and this one to another then you could hope that both accesses could occur in parallel, or at least that they would not compete, each one trying to bring the disk heads to read or write different cylinders. Things are much much more confused these days, with memory caches everywhere, virtual disks which are indeed little pieces of actual physical disks, etc. And I don't believe that we'll ever come back to a close match between what you 'see', and the actual hardware. In fact, everything is pointing in the opposite direction.  Just remember that redo logs are written sequentially, so if the disk heads could not move frantically it would be better, and that you have several of them needing to be written at the same time. Otherwise that rollback segments/undo tablespace and temporary segments are often heavily accessed. Have a look at V$FILESTAT and then try to do for the best, with directory structures which look logical to you (and, hopefully, to others).

Regards,

Stephane Faroult
Oriole

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Author: Stephane Faroult
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