Re: SAN/NAS options

Usually manufacturer's claims are tested in 'ideal' conditions, it may not translate well on bandwidth seen on the host side. A 2Gbps Fiber Channel connection would (ideally) give you about 250MB/sec per HBA. Not sure how it translates for GigE considering scsi protocol overheads, but you may want to confirm from them how they achieved 370MB/sec (hwo many iSCSI controllers, what file system, how many drives, what RAID type, block size, strip size, cache settings, etc), and whether it was physical I/O or cached. In other words, if someone has any benchmark numbers, that would be helpful.

Regarding diskless iscsi boots for future servers, remember that it's a shared storage, if you have a busy server attached to your Nexsan, you may have to think twice on sharing the performance (throughput and IOPS of the storage controller) without impacting the existing hosts, unless you are zizing it now.

And you want to have a pretty clean GigE network, more or less dedicated to this block traffic.

Large internal storage with more memory and AMD CPUs is an option as Luke had originally suggested. Check out Appro as well.

I'd also be curious to know if someone has been using this (SATA/iSCSI/SAS) solution and what are some I/O numbers observed.

Thanks,
Anjan

-----Original Message-----
From: Matthew Schumacher [mailto:matt(dot)s(at)aptalaska(dot)net]
Sent: Mon 12/19/2005 7:41 PM
To: pgsql-performance(at)postgresql(dot)org
Cc:
Subject: Re: [PERFORM] SAN/NAS options

Jim C. Nasby wrote:
> On Wed, Dec 14, 2005 at 01:56:10AM -0500, Charles Sprickman wrote:
> You'll note that I'm being somewhat driven by my OS of choice, FreeBSD.
>
>>Unlike Solaris or other commercial offerings, there is no nice volume
>>management available. While I'd love to keep managing a dozen or so
>>FreeBSD boxes, I could be persuaded to go to Solaris x86 if the volume
>>management really shines and Postgres performs well on it.
>
>
> Have you looked at vinum? It might not qualify as a true volume manager,
> but it's still pretty handy.

I am looking very closely at purchasing a SANRAD Vswitch 2000, a Nexsan
SATABoy with SATA disks, and the Qlogic iscsi controller cards.

Nexsan claims up to 370MB/s sustained per controller and 44,500 IOPS but
I'm not sure if that is good or bad. It's certainly faster than the LSI
megaraid controller I'm using now with a raid 1 mirror.

The sanrad box looks like it saves money in that you don't have to by
controller cards for everything, but for I/O intensive servers such as
the database server, I would end up buying an iscsi controller card anyway.

At this point I'm not sure what the best solution is. I like the idea
of having logical disks available though iscsi because of how flexible
it is, but I really don't want to spend $20k (10 for the nexsan and 10
for the sanrad) and end up with poor performance.

On other advantage to iscsi is that I can go completely diskless on my
servers and boot from iscsi which means that I don't have to have spare
disks for each host, now I just have spare disks for the nexsan chassis.

So the question becomes: has anyone put postgres on an iscsi san, and if
so how did it perform?

schu

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