Ok switch over complete. Let me know if you notice anything odd or slow and I'll tweak things a bit. In a nutshell, this afternoon we moved to SSDs from old-school spinning disks. Anyone who is a bit of a computer geek is welcome to read on...
More than a year ago we exported the images and attachments out of the database onto disk to alleviate the strain. That works for a while but does mean the disk is doing more work, especially for a forum - lots of small files read constantly and randomly, especially as visitors poke at backpages.
The numbers this morning showed the disk working a lot. Here are some benchmarks before and after the switch over to SSDs:
before, on HDD
dd if=/dev/zero of=/tmp/output conv=fdatasync bs=384k count=1k; rm -f /tmp/output
1024+0 records in
1024+0 records out
402653184 bytes (403 MB) copied, 130.21 s, 3.1 MB/s
now, on SSD
dd if=/dev/zero of=/tmp/output conv=fdatasync bs=384k count=1k; rm -f /tmp/output
1024+0 records in
1024+0 records out
402653184 bytes (403 MB) copied, 0.485917 s, 829 MB/s
A test which previously took more than 2 minutes now completes in < 0.5s. The disk performance on the server is now benchmarked at 267x faster so I think we'll be good on disk speed for hopefully a while. Next item to popup will probably be CPU (this change has helped there too).