Re: Advice sought : new database server

On 05/03/12, Craig James (cjames(at)emolecules(dot)com) wrote:
> 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

Thanks for this quick guide to using pgbenc. My 4-year old SCSI server
with 4 RAID10 disks behind an LSI card achieved the following on a
contended system:

-c -t TPS
5 20000 446
10 10000 542
20 5000 601
30 3333 647

These results seem pretty lousy in comparison to yours. Interesting.

--
Rory Campbell-Lange
rory(at)campbell-lange(dot)net

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