On Mon, Mar 5, 2012 at 10:56 AM, Craig James <cjames@emolecules.com> wrote:
> On Sun, Mar 4, 2012 at 10:36 AM, Rory Campbell-Lange
> <rory@campbell-lange.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
those numbers are stupendous for 8 drive sata. how much shared
buffers do you have?
merlin