I've been running flashcache for a while now on both SSD and ZRAM devices. There's definitely a big improvement under the right situation. One of the biggest improvements I've seen so far has been running it against an ext4 LVM2 partition running a minecraft server:
0 4194304 flashcache stats:
read hits(986945), read hit percent(63)
write hits(10820089) write hit percent(91)
replacement(524380) write replacement(963051)
write invalidates(0) read invalidates(1)
pending enqueues(0) pending inval(0)
disk reads(566463) disk writes(10820089) ssd reads(986945) ssd writes(12373057)
uncached reads(1) uncached writes(0), uncached IO requeue(0)
pid_adds(0) pid_dels(0) pid_drops(0) pid_expiry(0)
If you get high enough cache reads and writes then it makes a world of difference.
Would be nice to see some hard and fast numbers though.
I also replaced tmpfs with zramfs a while ago on and saw substantial improvements there as well.
Last edited by Haven; 09-29-2011 at 12:47 PM.