ZFS and power management

[Karl Denninger]

I'm curious if anyone has come up with a way to do this...

I have a system here that has two pools -- one comprised of SSD disks
that are the "most commonly used" things including user home directories
and mailboxes, and another that is comprised of very large things that
are far less-commonly used (e.g. video data files, media, build
environments for various devices, etc.)

The second pool has perhaps two dozen filesystems that are mounted, but
again, rarely accessed.  However, despite them being rarely accessed ZFS
performs various maintenance checkpoint functions on a nearly-continuous
basis (it appears) because there's a low level, but not zero, amount of
I/O traffic to and from them.  Thus if I set power control (e.g. spin
down after 5 minutes of inactivity) they never do.  I could simply
export the pool but I prefer (greatly) to not do that because some of
the data on that pool (e.g. backups from PCs) is information that if a
user wants to get to it it ought to "just work."

Well, one disk is no big deal.  A rack full of them is another matter. 
I could materially cut the power consumption of this box down (likely by
a third or more) if those disks were spun down during 95% of the time
the box is up, but with the "standard" way ZFS does things that doesn't
appear to be possible.

Has anyone taken a crack at changing the paradigm (e.g. using the
automounter, perhaps?) to get around this?

-- 
Karl Denninger
karl at denninger.net <mailto:karl at denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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