The primary goal is to reduce the number of seeks a disk or array has
to perform. Serial write throughput is much higher than random write
throughput. If you are performing very high volume throughput on a
server that is doing multiple things, then it maybe advisable to have
one partition for OS, one for postgresql binaries, one for xlog and
one for table data (or multiple if you are PG8.0). This is the
ultimate configuration, but most people don't require this level of
seperation. If you do need this level of seperation, also bare in
mind that table data writes are more likely to be random writes so you
want an array that can sustain a high levels of IO/sec, so RAID 10
with 6 or more drives is ideal. If you want fault tolerance, then
RAID 1 for OS and postgresql binaries is a minimum, and I believe that
xlog can also go on a RAID 1 unless you need more MB/sec. Ultimately
you will need to benchmark any configuration you build in order to
determine if it's successfull and meets your needs. This of course
sucks, because you don't want to buy too much because it's a waste of
$$s.
What I can tell you is my own experience which is a database running
with xlog, software and OS on a RAID 1, with Data partition running on
3 disk RAID 5 with a database of about 3 million rows total gets an
insert speed of about 200 rows/sec on an average size table using a
compaq proliant ML370 Dual Pentium 933 w/2G RAM. Most of the DB is in
RAM, so read times are very good with most queries returning sub
second.
Hope this helps at least a little
Alex Turner
NetEconomist
On Wed, 19 Jan 2005 09:03:44 +1100, Benjamin Wragg <bwragg@tpg.com.au> wrote:
>
> I just wanted to bounce off the list the best way to configure disks for a
> postgresql server. My gut feeling is as follows:
>
> Keep the OS and postgresql install on seperate disks to the postgresql /data
> directory?
> Is a single hard disk drive acceptable for the OS and postgresql program, or
> will this create a bottle neck? Would a multi disk array be more
> appropriate?
>
> Cheers,
>
> Benjamin Wragg
>
>
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