Re: lvm2 performance data with linux-2.6

[Bill Davidsen <davidsen@tmr.com>]

markw@osdl.org wrote:
> I've started collecting various data (including oprofile) using our
> DBT-2 (OLTP) workload with lvm2 on linux 2.6.2 and 2.6.3 on ia32 and
> ia64 platforms:
> 	http://developer.osdl.org/markw/lvm2/
> 
> So far I've only varied the stripe width with lvm, from 8 KB to 512 KB,
> for PostgreSQL that is using 8 KB sized blocks with ext2.  It appears
> that a stripe width of 16 KB through 128KB on the ia64 system gives the
> best throughput for the DBT-2 workload on a volume that should be doing
> mostly sequential writes.
> 
> I'm going to run through more tests varying the block size that
> PostgreSQL uses, but I wanted to share what I had so far in case there
> were other suggestions or recommendations.
> 
Here's one thought: look at the i/o rates on individual drives using 
each stripe size. You *might* see that one size does far fewer seeks 
than others, which is a secondary thing to optimize after throughput IMHO.

If you don't have a tool for this I can send you the latest diorate 
which does stuff like this, io rate perdrive or per partition, something 
I occasionally find revealing.

		-bill