Craig James wrote:
I'm testing/tuning a new midsize server and ran into an inexplicable problem. With an RAID10 drive, when I move the WAL to a separate RAID1 drive, TPS drops from over 1200 to less than 90!
Normally <100 TPS means that the write cache on the WAL drive volume is disabled (or set to write-through instead of write-back). When things in this area get fishy, I will usually download sysbench and have it specifically test how many fsync calls can happen per second. http://projects.2ndquadrant.com/talks , "Database Hardware Benchmarking", page 28 has an example of the right incantation for that.
Also, make sure you run 3ware's utilities and confirm all the disks have finished their initialization and verification stages. If you just adjusted disk layout that and immediate launched into benchmarks, those are useless until the background cleanup is done.
-- Greg Smith 2ndQuadrant US Baltimore, MD PostgreSQL Training, Services and Support greg@xxxxxxxxxxxxxxx www.2ndQuadrant.us -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
