I have a brand new server w/48G RAM which I am going to use as a DB server. I don't expect problems with disk reads, but I definitely would like to optimize for write intensive load patterns.
The OS is RHEL 5.6 and the FS is ext3, I've added "noatime" and "data=writeback" to /etc/fstab already and the latter option helped to reduce LA a lot. My next goal is to optimize the pdflush process wherever possible. I tried to apply tweaks mentioned here, but to no avail. Probably this information is just outdated.
What are my further options? Should I continue experimenting with pdflush or maybe it's better just to leave it as is? I tend to lower
dirty_background_ratio sysctl values to increase I/O smoothness but these values seem to be not related to performance, the load pattern in Munin under stress test is basically the same.
Should I also try different I/O scheduler? Can I benefit from having lots of RAM in a write intensive setup at all? I understand that disk I/O speed and latency are nothing to do with the RAM, but my goal is not to magically write to disk faster, but to increase system stability and to implement some kind of graceful degradation.
Let's say I have good backups and can accept further data consistency tradeoffs like "data=writeback".