On Wed, Mar 27, 2013 at 3:08 PM, Stan Hoeppner [off-list ref] wrote:

On 3/27/2013 4:06 PM, Mark Knecht wrote:

quoted

All that said, I still don't really know if I was starting over today
how to choose a new chunk size. That still eludes me. I've sort of
decided that's one of those things that make you guys pros and me just
a user. :-)

Chunk size is mostly dictated by your workload IO patterns, and the
number and latency of your spindles.

Is there a way for me to measure, say over a whole day or some fixed
time, what the workload really looks like?

The machine is a basic Gentoo desktop machine running KDE. The only
workload where I really care about performance is that I run a bunch
of Virtualbox Win 7 & Win XP VMs where I need to the performance to be
as good as I can reasonably get. The problem I have is these VMs are
either 1 huge file (40-50GB in a single file) or many 2GB files. I
haven't a clue how Windows & Virtualbox is accessing what it sees as a
virtual drive and then underlying that how the vbox drivers are using
the system to get to the RAID.

It would be interesting to set some program running, probably on a
weekend or sometime when performance isn't so critical, and see what
sort of data gets collected, assuming there's a program that does that
sort of thing.

Thanks,
Mark