Janning wrote:
IMHO it is looking quite fast compared to the values mentioned in the article.
The tests in the article were using the 2006 versions of the same drive you have, so I'd certainly hope yours are faster now.
What values do you expect with a very expensive setup like many spindles, scsi, raid controller, battery cache etc. How much faster will it be?
If you visit look at my "Database Hardware Benchmarking" talk at http://projects.2ndquadrant.com/talks I give examples of some of this. Page 9 shows how much of a speedup I saw going from one cheap drive to three for example, and P32 shows that in the mixed I/O bonnie++ seeks tests tripling the number of drives increases the seeks rating it computes from 177 to 371.
If you add in a RAID controller, the sequential read/write numbers increase no differently than if you add disks with software RAID. They do significantly increase what I call the "Commit Rate", which is how many small writes you can get per second for database commits. The commit rate for regular drives is proportional to their rotation rate, between 100-250 commit/second without a battery-backed RAID controller. As you can also see on P32, it jumps to thousands of commits/second with one.
Presuming you have reasonable sequential performance and a battery-backed controller to make the commit rate reasonable, database applications will then normally bottleneck at how fast they can seek around. It is extremely hard to estimate how fast that scales upwards as you add more disks to an array and insert a read/write cache into the system.
-- Greg Smith 2ndQuadrant US Baltimore, MD PostgreSQL Training, Services and Support greg@xxxxxxxxxxxxxxx www.2ndQuadrant.us -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
