[Arjen van der Meijden]
> Your SAN-pusher should have a look at the HP-submissions for TPC-C...
> The recent Xeon systems are all without SAN's and still able to connect
> hundreds of SAS-disks.
Yes, I had a feeling that the various alternative solutions for "direct
connection" hadn't been investigated fully. I was pushing for it, but
hardware is not my thing. Anyway, most likely the only harm done by
chosing SAN is that it's more expensive than an equivalent solution with
direct connected disks. Well, not my money anyway. ;-)
> Obviously its a bit difficult to share those 628 harddrives amongst
> several systems, but the argument your colleagues have for SAN isn't a
> very good one.
As far as I've heard, you cannot really benefit much from this with
postgres, one cannot have two postgres servers on two hosts sharing the
same data (i.e. using one for failover or for CPU/memory-bound read
queries).
Having the SAN connected to several hosts gives us two benefits, if the
database host goes down but not the SAN, it will be quite fast to start
up a new postgres instance on a different host - and it will also be
possible to take out backups real-time from the SAN without much
performance-hit. Anyway, with a warm standby server as described on
http://www.postgresql.org/docs/current/interactive/warm-standby.html one
can achieve pretty much the same without a SAN.