Re: Advice sought : new database server

On Sun, Mar 4, 2012 at 2:58 AM, Rory Campbell-Lange
<rory(at)campbell-lange(dot)net> wrote:
> I'd be grateful for advice on specifying the new server
>
> We presently have one main database server which is performing well. As
> our services expand we are thinking of bringing another database server
> to work with it, and back each up via Postgres 9.1 streaming replication
> each to a VM server -- at present we are doing pg_dumps twice a day and
> using Postgres 8.4.
>
> The existing server is a 2 x Quad core E5420 Xeon (2.5GHz) with 8GB of
> RAM with an LSI battery-backed RAID 10 array of 4no 10K SCSI disks,
> providing about 230GB of usable storage, 150GB of which is on an LV
> providing reconfigurable space for the databases which are served off an
> XFS formatted volume.
>
> We presently have 90 databases using around 20GB of disk storage.
> However the larger databases are approaching 1GB in size, so in a year I
> imagine the disk requirement will have gone up to 40GB for the same
> number of databases. The server also serves some web content.
>
> Performance is generally good, although we have a few slow running
> queries due to poor plpgsql design. We would get faster performance, I
> believe, by providing more RAM. Sorry -- I should have some pg_bench
> output to share here.

RAM is always a good thing, and it's cheap enough that you can throw
32 or 64G at a machine like this pretty cheaply.

> I believe our existing server together with the new server should be
> able to serve 200--300 databases of our existing type, with around 100
> databases on our existing server and perhaps 150 on the new one. After
> that we would be looking to get a third database server.
>
> I'm presently looking at the following kit:
>
>    1U chassis with 8 2.5" disk bays
>    2x Intel Xeon E5630 Quad-Core / 4x 2.53GHz / 12MB cache
>    8 channel Areca ARC-1880i (PCI Express x8 card)
>      presumably with BBU (can't see it listed at present)
>    2 x 300GB SAS  2.5" disks for operating system
>      (Possibly also 300GB SATA VelociRaptor/10K RPM/32MB cache
>      RAID 1
>    4 x 300GB SAS  2.5" storage disks
>      RAID 10
>    48.0GB DDR3 1333MHz registered ECC (12x 4.0GB modules)
>
> My major question about this chassis, which is 1U, is that it only takes
> 2.5" disks, and presently the supplier does not show 15K SAS disk
> options. Assuming that I can get the BBU for the Areca card, and that
> 15K SAS disks are available, I'd be grateful for comments on this
> configuration.

The 15k RPM disks aren't that big of a deal unless you're pushing the
bleeding edge on a transactional system. I'm gonna take a wild guess
that you're not doing heavy transactions, in which case, the BBU on
the areca is the single most important thing for you to get for good
performance. The areca 1880 is a great controller and is much much
easier to configure than the LSI. Performance wise it's one of the
fastest DAS controllers made.

If the guys you're looking at getting this from can't do custom
orders, find a white box dealer who can, like www.aberdeeninc.com. It
might not be on their site, but they can build dang near anything you
want.