Re: opinion on disk speed

On Fri, 09 Dec 2005 09:15:25 -0500
"Jeremy Haile" <jhaile(at)fastmail(dot)fm> wrote:

> > one other note, you probably don't want to use all the disks in a
> > raid10 array, you probably want to split a pair of them off into a
> > seperate raid1 array and put your WAL on it.
>
> Is a RAID 1 array of two disks sufficient for WAL? What's a typical
> setup for a high performance PostgreSQL installation? RAID 1 for WAL
> and RAID 10 for data?
>
> I've read that splitting the WAL and data offers huge performance
> benefits. How much additional benefit is gained by moving indexes to
> another RAID array? Would you typically set the indexes RAID array up
> as RAID 1 or 10?

Yes most people put the WAL on a RAID 1 and use all the remaining
disks in RAID 10 for data.

Whether or not moving your indexes onto a different RAID array is
worthwhile is harder to judge. If your indexes are small enough
that they will usually be in ram, but your data is to large to
fit then having the extra spindles available on the data partition
is probably better.

As always, it is probably best to test both configurations to see
which is optimal for your particular application and setup.

---------------------------------
Frank Wiles <frank(at)wiles(dot)org>
http://www.wiles.org
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