Re: PostgreSQL data on a NAS device ? - Mailing list pgsql-performance

Thanks for your reply, Jeff.

If we are going to use a NAS device for storage, then it will be attached
through a gigabit ethernet connection. Fiber will not be an option, since
that would negate the savings we can make by using an IDE NAS device instead
of SCSI-RAID, fiber's pretty expensive, right?

Using a NAS device (that is used only by PostgreSQL, so it's dedicated) with
3Gb of RAM and four 7200 rpm IDE harddisks, connected using a gigabit
ethernet connection to the PostgreSQL server, do you think it will be a
match for a SCSI-RAID config using 4 or 6 15000rpm disks (RAID-10) through a
SCSI-RAID controller having 128mb of writeback cache (battery-backed)?

The SCSI-RAID config would be a lot more expensive. I can't purchase both
configs and test which one wil be faster, but if the NAS solution would be
(almost) as fast as the SCSI-RAID solution, it would be cheaper and easier
to maintain...

About clustering: I know this can't be done by hooking multiple postmasters
to one and the same NAS. This would result in data corruption, i've read...

Kind regards,
Alexander.


----- Original Message -----
From: "Jeff" <threshar@torgo.978.org>
To: "Alexander Priem" <ap@cict.nl>
Cc: <pgsql-performance@postgresql.org>
Sent: Monday, October 20, 2003 2:20 PM
Subject: Re: [PERFORM] PostgreSQL data on a NAS device ?


> On Mon, 20 Oct 2003 09:12:35 +0200
> "Alexander Priem" <ap@cict.nl> wrote:
>
> > I am asking this because a NAS device is much cheaper to set up than a
> > couple of SCSI disks. I would like to use a relatively cheap NAS
> > device which uses four IDE drives (7.200 rpm), like the Dell
> > PowerVault 725N. The disks themselves would be much slower than SCSI
> > disks, I know, but a NAS device can be equipped with 3 Gb of memory,
> > so this would make a very large disk cache, right? If this NAS would
> > be dedicated only to PostgreSQL, would this be slower/faster than a
> > SCSI RAID-10 setup of 6 disks? It would be much cheaper...
> >
>
> The big concern would be the network connection, unless you are going
> fiber.  You need to use _AT LEAST_ gigabit. _at least_.    If you do
> go that route it'd be interesting to see bonnie results.  And the
> other thing - remember that just because you are running NAS doesn't
> mean you can attach another machine running postgres and have a
> cluster.  (See archives for more info about this).
>
> I suppose it all boils down to your budget (I usually get to work with
> a budget of $0). And I mentioned this in another post- If you don't mind
> refurb disks(or slightly used) check out ebay - you can get scsi disks
> by the truckload for cheap.
>
>
> --
> Jeff Trout <jeff@jefftrout.com>
> http://www.jefftrout.com/
> http://www.stuarthamm.net/