On Sun, Mar 4, 2012 at 10:36 AM, Rory Campbell-Lange < r...@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 Craig
