Since the commitlog/WAL is sequential-write, does it mattert that much to put it in ssd ?(i understand that it matters to put it in separate disk-subsystem so the write/read patterns don't interfere)
On Tue, May 06, 2014 at 11:13:42AM +0200, Johann Spies wrote:
Analysis or the SAR-logs showed that there were too much iowait in the CPU's on the old system which has a lower spec CPU than the ones considered for the new system.
iowait means the cpu is doing nothing but waiting for data from the disk. buying faster cpus means that they will be able to spend more time waiting for data from the disk. you'd probably get much better bang for the buck upgrading the storage subsystem than throwing more money at cpus.
with enough disk space - about 4.8 Tb on RAID 10. My question is about the possible advantage and usage of SSD disks in the new server.
At the moment I am considering using 2 x 200GB SSD' s for a separate partion for temporary files and 2 x 100GB for the operating system.
If you're talking about SSDs for the OS, that's a complete waste; there is essentially no I/O relating to the OS once you've booted.
So my questions:
1. Will the SSD's in this case be worth the cost? 2. What will the best way to utilize them in the system?
The best way to utilize them would probably be to spend less on the CPU and RAM and more on the storage, and use SSD either for all of the storage or for specific items that have a high level of I/O (such as the indexes). Can't be more specific than that without a lot more information about the database, how it is utilized, and what's actually slow.
