dushy wrote: > Iam running a postgresql 9.0.13 master/slave instance in a write heavy > workload. > > The hardware is a Dell 720, E5530 - 8 core, 128GB RAM. The database (around > 250g with indexes/bloat etc) is sitting on flashcache device with 2 fusion- > io PCIe MLC SSDs as frontend and a MD3200 based RAID10 (14*1TB SATA disks) > as backend. OS is centos 6.2 with kernel 2.6.32-431.20.3.el6.x86_64. > > Currently, the performance related configuration is mostly default i,e > shared_buffers, > effective_cache_size. The only directive that seems different is > checkpoint_segments = 96 > > Iam moving to postgresql 9.3 shortly and planning to tune the above > directives as below.. > > effective_cache_size = 100GB # free+buffers is pretty consistent around 110 > to 120GB and pg_oscache_total is around 80GB consistently > checkpoint_segments = 32 # 96 seems to long and all flushes seem to be only > due to checkpoint_timeout > > Additionally iam turning off THB defrag as suggested by some posts on the > lists. Though, My initial pgbench testing doesn't seem to indicate any > issues with THB defrag turned on/off. > > Iam not sure about shared_buffers and wal_buffers - iam inclined to leave > them to defaults. But based on this article > (http://rhaas.blogspot.in/2012/03/tuning-sharedbuffers-and-walbuffers.html) > it looks there will be some advantages in tuning it > > What would be a good value for shared_buffers and wal_buffers ? > > Please let me know if additional information will help. The frequently heard advice for setting shared_buffers is 25% of RAM, but with memory as big as that that may be too much (it can lead to checkpoint I/O spikes and greater overhead in managing shared buffers). Try with something like 8 or 16 GB. Ideally you should test, use pg_buffercache to inspect shared buffers and see what setting works best for you. Set wal_buffers to 16MB so that a whole WAL segment will fit. The best tuning strategy would be to stuff another 128 GB RAM into the machine and have your DB in RAM. Yours, Laurenz Albe -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
