Re: RAIDframe performance vs. stripe size

[Greg Oster <oster%cs.usask.ca@localhost>]

On Thu, 10 May 2012 13:23:24 -0400
Thor Lancelot Simon <tls%panix.com@localhost> wrote:

> On Thu, May 10, 2012 at 11:15:09AM -0600, Greg Oster wrote:
> > 
> > What you're typically looking for in the parallelization is that a
> > given IO will span all of the components.  In that way, if you have
> > n
> 
> That's not what I'm typically looking for.  You're describing the
> desideratum for a maximum-throughput application.  Edgar is describing
> the desideratum for a minimum-latency application.  No?

I think what I describe still works for minimum-latency too...  where
it doesn't work is when your IO is so small that the time to actually
transfer the data is totally dominated by the time to seek to the data.
In that case you're better off in just going to a single component
instead of having n components all moving their heads around to grab
those few bytes (especially true where there are lots of simultaneous
IOs happening).

Of course, this is all still theoretical -- the best thing is to
experiment with different RAID settings and real workloads to see what
works best for the particular applications...

Later...

Greg Oster