Re: [OT] RAID controllers blocking one another?

From: "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com>
To: "Sean Davis" <sdavis2(at)mail(dot)nih(dot)gov>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: [OT] RAID controllers blocking one another?
Date: 2008-01-17 21:07:02
Message-ID: dcc563d10801171307p4869b0ayc27c3433c19455ba@mail.gmail.com
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On Jan 17, 2008 2:17 PM, Sean Davis <sdavis2(at)mail(dot)nih(dot)gov> wrote:
> We have a machine that serves as a fileserver and a database server. Our
> server hosts a raid array of 40 disk drives, attached to two3-ware cards,
> one 9640SE-24 and one 9640SE-16. We have noticed that activity on one
> controller blocks access on the second controller, not only for disk-IO but
> also the command line tools which become unresponsive for the inactive
> controller. The controllers are sitting in adjacent PCI-express slots on a
> machine with dual-dual AMD and 16GB of RAM. Has anyone else noticed issues
> like this? Throughput for either controller is a pretty respectable
> 150-200MB/s writing and somewhat faster for reading, but the "blocking" is
> problematic, as the machine is serving multiple purposes.
>
> I know this is off-topic, but I know lots of folks here deal with very large
> disk arrays; it is hard to get real-world input on machines such as these.

Sounds like they're sharing something they shouldn't be. I'm not real
familiar with PCI-express. Aren't those the ones that use up to 16
channels for I/O? Can you divide it to 8 and 8 for each PCI-express
slot in the BIOS maybe, or something like that?

Just a SWAG.

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