Re: Optimizing disk throughput on quad Opteron

> -----Original Message-----
> From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-
> owner(at)postgresql(dot)org] On Behalf Of John Philips
> Sent: Monday, October 23, 2006 8:17 AM
> To: Ben Suffolk
> Cc: pgsql-performance(at)postgresql(dot)org
> Subject: Re: [PERFORM] Optimizing disk throughput on quad Opteron
>
> > The thing I would ask is would you not be better
> > with SAS drives?
> >
> > Since the comments on Dell, and the highlighted
> > issues I have been
> > looking at HP and the the Smart Array P600
> > controller with 512 BBWC.
> > Although I am looking to stick with the 8 internal
> > disks, rather than
> > use external ones.
> >
> > The HP Smart Array 50 is the external array for SAS
> > drives. Not
> > really looked into it much though.
>
> Ben,
>
> The Smart Array 50 supports a maximum of 10 disks and
> has a single I/O module, while the Smart Array 30
> supports up to 14 disks and can be configured with a
> dual I/O module.
>
> I was under the assumption that SAS runs at the same
> speed as Ultra320, in which case the Smart Array 30 is
> a better bet...
>
> Thanks for your feedback.

The drives might be about the same speed, but SAS is a completely
different bus architecture from SCSI. U320 is a parallel interface
limited to 320 MB/s for the total bus (160 MB/s per channel, so be
careful here). SAS is a 3.0Gbps direct serial interface to the drive.
So, after 5-6 drives, SAS will definitely start to pay off. Take a look
at Dell's MD1000 external enclosure vs the previous version. The MD1000
offers much better performance (not saying to go with dell, just giving
an example of SCSI vs. SAS from a vendor I'm familiar with). Oh, and if
you're not completely against dell, you can daisy chain 3 of the MD1000
enclosures together off one of their new 6850 (Quad Woodcrest) or 6950
(Quad Operton).

At the moment, the Woodcrests seem to be outperforming the Opteron in
server benchmarks, I have a quad core (dual cpu) 2950 I'd be happy to
run some pg_benches (or other preferred benchmark) if someone has a
similar opteron so we can get some relevant comparisons on the list.

Also, here's a link that was posted a while back on opteron vs.
woodcrest:
http://tweakers.net/reviews/646

HTH,

Bucky