Re: Advice sought : new database server

On Sun, Mar 4, 2012 at 10:36 AM, Rory Campbell-Lange <
rory(at)campbell-lange(dot)net> wrote:

> We do have complex transactions, but I haven't benchmarked the
> performance so I can't describe it. Few of the databases are at the many
> million row size at the moment, and we are moving to an agressive scheme
> of archiving old data, so we hope to keep things fast.
>
> However I thought 15k disks were a pre-requisite for a fast database
> system, if one can afford them? I assume if all else is equal the 1880
> controller will run 20-40% faster with 15k disks in a write-heavy
> application. Also I would be grateful to learn if there is a good reason
> not to use 2.5" SATA disks.
>

Without those benchmarks, you can't really say what "fast" means. There
are many bottlenecks that will limit your database's performance; the
disk's spinning rate is just one of them. Memory size, memory bandwidth,
CPU, CPU cache size and speed, the disk I/O bandwidth in and out, the disk
RPM, the presence of a BBU controller ... any of these can be the
bottleneck. If you focus on the disk's RPM, you may be fixing a bottleneck
that you'll never reach.

We 12 inexpensive 7K SATA drives with an LSI/3Ware 9650SE and a BBU, and
have been very impressed by the performance. 8 drives in RAID10, two in
RAID1 for the WAL, one for Linux and one spare. This is on an 8-core
system with 12 GB memory:

pgbench -i -s 100 -U test
pgbench -U test -c ... -t ...

-c -t TPS
5 20000 3777
10 10000 2622
20 5000 3759
30 3333 5712
40 2500 5953
50 2000 6141

Craig