Sebastian Böhm wrote:
> I consider buying one of these Intel SSDs for my Database (MLC).
> .....
> currently I have a lot of small random reads/writes causing heavy iowait.
how many r/s and w/s in `iostat -x 5` while your database is humming are
you seeing now? Thats the single key performance factor in disk bound
database IO. Caches can reduce the r/s requirements but the writes have
to go to disk if you want data integrity. ok, a raid controller with
battery back cache configured for writeback can accelerate the writes by
a lot too.
a desktop 7200 rpm SATA drive will saturate at under 100 IO ops/sec max
with the typical 8kbyte random blocks of a database, while a 15k server
drive can sustain 200 io/sec, and a raid 1+0 can hit several times more
(I've seen sustained 200/s on each of 4 15k spindles) while still using
normal hard disks. Those intel SSDs are supposed to be good for 1000
or so IOP/sec if I remember correctly... (of course, in a mirror, you
have to half the aggregated writes for the true number of useful random
writes)