Raidframe and disk strategy

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        hello.  I've been looking at some disk performance issues lately and
trying to figure out if there's anything I can do to make it better.  (This
is under NetBSD/I386 5.1_stable with sources from July 18 2012).  During
the course of my investigations, I discovered the raidframe driver does not
implement the DIOCSSTRATEGY or DIOCGSTRATEGY ioctls.  Even more
interestingly, I notice its set to use the fcfs strategy, and has been
doing so since at least NetBSD-2.0.  The ccd(4) driver does the same thing.
Presumably, the underlying disks can use what ever strategy they use for
handling queued data, but I'm wondering if there is a particular reason the
fcfs strategy was chosen for the raidframe driver as opposed to letting the
system administrator pick the strategy?  My particular environment has a
lot of unrelated reads and writes going on simultaneously, and it occurrs
to me that using a different disk strategy than fcfs might mitigate some of
these issues.  Were bench marks done to pick the best strategy for
raidframe and/or ccd or is there some other eason I'm missing that
implementing a buffer queue strategy on top of these devices is a bad idea?
-thanks
-Brian