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Optimal Disk Layout??

From: Walter K <>
Date: Fri, 21 Sep 2001 06:14:40 -0700
Message-ID: <>


I'm encuntering a relatively high iowait percentage when my hot backups are running. The platform is Sun
(E420 2cpu running SunOS 5.7) with an A1000 disk array
(8 9Gb drives, hardware Raid-5). The array is one
volume and all DB components (redo, archive, data, index, system, etc.) are on the same volume except for the binaries. The database is not large, only ~8Gb in size and the transactional volume is not much either. However, when the backups run, the iowait according to 'top' hovers between 50-70% which causes our application to time-out via Web Logic 6.0.

The developers can't explain why the timeouts are occurring (WLS 6.0 is a new upgrade from 5.1). The SysAdmin isn't much help either.

I have an opportunity to rebuild the database on another machine and use RAID 1+0 -- the thought being that we are choking ourselves with Raid-5 when the hot backups are performing the cp's (copies) and then the files are compressed.

My first question is, how is the data distributed across the drives in my Raid-5 configuration? Is each disk being filled contiguously in series or is the data being spread around in a pseudo-striping manner?

My second question/dilema is, the new array (another A1000) will have 6 18Gb drives and with Raid 1+0 that shrinks to 3 drives of usable space for everything except redo and archive. 4 9Gb drives will be added in two mirrored sets, one for redo and the other for archive. I'm afraid that I will see worse I/O performance with the new array because it has so fewer physical drives, thus eliminating the benefit of not having to write the parity info.

Do you concur? Knowing the two arrays I have to work with, which would be the better configuration?

Any suggestions, recommendations would VERY much be appreciated.

Thanks again for the feedback.

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Author: Walter K

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Received on Fri Sep 21 2001 - 08:14:40 CDT

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