Server choice.

[Alex Hayward]

On Thu, 20 Apr 2006, Paul Halliday wrote:

> Hi,
>
> I am in the process of building a new database server and after
> pricing up 2 Dell models I thought I would throw this out just to see
> which choice would be better suited for FreeBSD.

You didn't say what database you're running.

Certain Poweredges (6650s at least) have a rather poor repute on the
PostgreSQL mailings (for running PostgreSQL, at least). You may wish to
check the archives before buying one. We used to use a 6650 for running
PostgreSQL and the performance wasn't all that good for our application.
Our database is much more CPU and memory-bandwidth bound than IO bound,
though.

For a database you probably want Opterons, not Pentiums. We've found them
to perform extremely well (Athlons do well too). Your 'Dell only'
restriction may well cost you a lot of performance (unless Dell have
started using Opterons while I wasn't looking, or unless I'm out of date
on the performance of Pentiums).

> The demands on the system will be mostly network -> disk I/O with a
> hope of best performance on quickly servicing numerous reads; for
> example when reports are generated using the data in the database.
>
> The 2 choices (we dont have that much money and they have to be Dell)
> are a poweredge 1850 and a poweredge 850.
>
> 850 specs.
> ----------------
> Procsesor: Pentium(Dual Core) 830 @ 3.0GHz/2X1MB Cache 800MHz FSB
> Memory: 2GB DDR2, 533MHz (2x1GB) Dual ranked DIMMs
> Disks: SATA
>
> 1850 specs.
> ------------------
> Processors: 2 @ Xeon @ 3.0GHz/2MB Cache 800MHz FSB
> Memory: 2GB DDR2, 400MHz (4x512) Single ranked DIMMs
> Disks: Ultra 320
>
> The pricing is really close.

I presume that it's some sort of decision support/data mining
application, that there's no hope of fitting much of your data in to RAM
and that there's no hope of beating the 'Dell only' restriction's
originator in to submission.

I'd go for the 1850 and lots and lots of fast disks in a RAID 10 array.
AFAICS there are only two slots in a 1850. Hmm, it looks like 850s have
only two, too. Do you intend to use an external disk array, or are your IO
requirement just not that high? If not make sure you get the fastest disks
available (it looks like the 1850 can come with 15kRPM drives, whereas the
850 SATA ones are 7.4 - which should pretty much kill that option), two
disks isn't many.

If you're doing any significant writes then make sure you get and enable
the battery-backed cache on the RAID card to avoid having an fsync flush
data all the way to disk at the end of every transaction. Does the 850
even have one? That'd be another good reason to get a 1850...