Joga,
I disagree with your 'Before tuning RDBMS and SQL,'. Tune SQL first,
then tune your SGA. I/O bottlenecks often are a consequence of too much
I/Os which are themselves a consequence of poorly written SQL. Assume
you are regularly scanning some mega-table, just avoiding it may
magically solve your I/O problem ...
Next, try to play with buffer pools, to keep the really useful data in
memory. Check and monitor closely how much shared pool you need. Check
the frequency of you redo log switches - remember that they trigger
checkpoints, in other words I/Os.
That said, having everything on one logical volume is pretty hard to
manage. I fully agree with I can't remember whom who some time ago was
complaining about the lack of visibility of logical volumes - it's
somewhat easier when you know that this filesystem is on this spindle
which you access through this controller. Typically, I would do whatever
I can to separate redo log archives from the rest. For one thing, they
do not need the same redundancy and safety level as the rest. And they
probably cause much of the I/O.
If you are working in archive log mode and have a proper backup
scheme, I would not be paranoid about redundancy. Many people, possibly
because they do not fully understand what they may need in case of
recovery, tend to go for belt, braces, parachute, plus special insurance
policy. I have no special knowledge of IBM enhanced RAID1, but I would
try to have datafiles on mirrored disks, safely spread control files and
redo log groups, and stop worrying about the rest ...
--
Regards,
Stephane Faroult
email: sfaroult_at_oriolecorp.com
Oriole Corporation
Voice: +44 (0) 7050-696-269
Fax: +44 (0) 7050-696-449
Performance Tools & Free Scripts
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>
> I advised the client to replace RAID5 with RAID0 + 1.
> Unfortunately Hardware does not support. IBM guy clarified this.
>
> The client does not want to spend any amount for additional disks.
> I left with two options :
> 1. To go for IBM enhanced RAID1 (striping + mirror)
> 2. Live with RAID5
> In the above cases, Please suggest me for suitable database layout
> which will
> give improve present bottleneck of disk I/0 .
> Before tuning RDBMS and SQL, I would like to come to baseline
> compromise with database layout.
>
> Does any one had came across RAID Enahanced 1 ...?
>
> I am new to Win NT on these boxes and RAID technology. Your help is
> very much appreciated.
>
>
> Regards
> Joga
>
> --
Received on Fri May 26 2000 - 08:44:12 CDT
