Re: SSD performance

I somehow managed to convince the powers that be to let me get a
couple X25-E's.
I tossed them in my macpro (8 cores), fired up Ubuntu 8.10 and did
some testing.

Raw numbers are very impressive. I was able to get 3700 random seek
+read's a second. In a R1 config it stayed at 3700, but if I added
another process it went up to 7000, and eventually settled into the
4000s. If I added in some random writing with fsyncs to it, it
settled at 2200 (to be specific, I had 3 instances going - 2 read-only
and 1 read-20% write to get that). These numbers were obtained
running a slightly modified version of pgiosim (which is on
pgfoundtry) - it randomly seeks to a "block" in a file and reads 8kB
of data, optionally writing the block back out.

Now, moving into reality I compiled 8.3.latest and gave it a whirl.
Running against a software R1 of the 2 x25-e's I got the following
pgbench results:
(note config tweaks: work_mem=>4mb, shared_buffers=>1gb, should
probably have tweaked checkpoint_segs, as it was emitting lots of
notices about that, but I didn't).

(multiple runs, avg tps)

Scalefactor 50, 10 clients: 1700tps

At that point I realized write caching on the drives was ON. So I
turned it off at this point:

Scalefactor 50, 10 clients: 900tps

At scalefactor 50 the dataset fits well within memory, so I scaled it
up.

Scalefactor 1500: 10 clients: 420tps

While some of us have arrays that can smash those numbers, that is
crazy impressive for a plain old mirror pair. I also did not do much
tweaking of PG itself.

While I'm in the testing mood, are there some other tests folks would
like me to try out?

--
Jeff Trout <jeff(at)jefftrout(dot)com>
http://www.stuarthamm.net/
http://www.dellsmartexitin.com/