On Sun, Mar 4, 2012 at 10:36 AM, Rory Campbell-Lange <rory@xxxxxxxxxxxxxxxxxx> 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
