Re: Best RAID configuration

In article <vfSX3.2985$MZ.21783_at_ozemail.com.au>,   "Richard Baker" <rbaker_at_quiktrak.com.au> wrote:
> Thanks for the inciteful info. I'll take my chances with a 3 disk
stripe
> set for the moment. I plan on mirroring the database to another
server, so
> that'll be my contingency. Run Oracle on the B/U server till primary
is
> fixed up
>
> I'll assume that the log files and ARC files should go onto the non-
RAID 5
> area of a disk as this is sequential writes.
>
> Thanks again.
>
> R. Baker
>
>

Conventional wisdom says to put log and archive files on non-striped disks, and separate from disks holding data, because of the sequential nature of these files. However, if these are on the same physical devices as your data, and you are supporting multiple databases, it would seem that there is nothing to be gained (from a pure performance standpoint) in doing this. As long as they are on the same physical device, they are still competing with data files for head positioning. Even if you do physically separate them from the data files and put them on a non-strip disk, if you have log files from multiple databases you still end up losing the performance gain of pure sequential writes. Not that there aren't some good arguments for doing this anyway, but don't lose sight of what the rational is and what's really going on at the physical level. We have up to 8 different test databases on one server. Even though their log files are going to a separate logical drive (even if it were a separate physical drive!) there's no way that drive would be spinning out pure sequential writing. It's bouncing all over, serviceing a log write from one database, then another database ...
--
Ed Stevens
(Opinions are not necessarily those of my employer)

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Before you buy. Received on Mon Nov 15 1999 - 09:18:01 CST