> We are running into issues with IO saturation obviously.  Since this
> thing is only going to get bigger we are looking for some advice on 
> how to accommodate DB's of this size.
<snip>
> Second and more radical, has anyone run 
> postgreSQL on the new Apple G5 with an XRaid system?  This seems like 
> a great value combination.  Fast CPU, wide bus, Fibre Channel IO, 
> 2.5TB all for ~17k.
<snip>
If you are going for I/O performance you are best off with one of the
Xserve competitors listed at http://www.apple.com/xserve/raid/.  The
Xserve is based on IDE drives which have a lower seek time (say 8.9 ms)
compared to scsi (3.6 ms for seagate cheetah).  For small random
read/write operations (like databases) this will give you a noticable
improvement in performance over ide drives.  Also make sure to get as
many drives as possible, more spindles equals better I/O performance.

> I keep see references to terabyte postgreSQL installations, I was
> wondering if anyone on this list is in charge of one of those and can 
> offer some advice on how to position ourselves hardware wise.

I've gone to about half terabyte size and all I can say is you should
plan for at least one quarter to one half a rack of drivespace (assuming
14 drives per 4u that's 42 to 84 drives).  Do yourself a favor and get
more rather than less, you will really appreciate it.  I averaged about
2 mb/s average per drive via the raid controller stats on 14 drive array
during I/O bound seek and update operations in 2 raid 10 arrays (half
xlogs and half data).  That comes out to around 2 hours for a terabyte
with 70 drives assuming a constant scaling.  You may be able to get more
or less depending on your setup and query workload.

> Thanks.
>
> --sean
>
>
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