Re: OFA Architecture with RAID

Well, not really. The problem with RAID5 arrays is their generally very poor write performance. Of the 3 RAID5 arrays I've tested this has been 50-200% slowdown compared to tqking the same drives in a striped array (i.e. RAID0). A write cache can get round this, but this is a dangerous route to take if you lose power to the server - potential database screw-up.

The problem is that much of your database may actually be very write intensive, especially redo, archive, temp and maybe your datafiles if that's what your application is like. Distributing the I/O is good, but mixing eveything together and hoping that the RAID5 array mix will some how sort it all out is not the way to go. A database's I/O is a far more complex mix, and you've got to be prepared to make some intelligent loaction decisions.

Like I said, best thing is to try it and monitor it. Start moving things around when you see bottlenecks and then re-monitor.

Regards,

Steve Phelan

(Oracle 7 & 8 OCP)

gremlin wrote:

> Well, that was my thinking with the one mount point. If the file system is RAID (5 or 3)
> then you really don't get anything by having different mount points, they all end up as
> one in the end anyway! I would think this would give very good performance, if you have
> n physical drives and n processors then the I/O is distributed as much as you can get it,
> isn't it? If you split it up (say, index tables on 2 drives and data tables on 3
> others?) then you still wait for the slowest one anyway I would think. Not that I claim
> to be any kind of expert.
>

[snip] Received on Sat Feb 27 1999 - 03:44:59 CST