Re: Spare drive won't spin down

[Neil Brown <neilb@suse.de>]

On Mon, 17 May 2010 17:38:04 -0700
Michael Evans <mjevans1983@gmail.com> wrote:

> You should make it a sysfs controllable option to keep the counter
> updated on spare discs or not.  The default can be to keep it within
> one as you currently are patching it to.  Then later you can change
> the default to the higher performance setting.  Better, the presence
> of that file can be used to test if the kernel supports it, and if it
> doesn't initramfs scripts can react accordingly.

There really isn't any need for user-space to know - this is an entirely
in-kernel thing.  mdadm already supports assembling arrays with widely
different event_counts.  It just gives them to the kernel and lets it make
the final decision.

And I think it is stretching things to call this a performance setting.  It
only changes behaviour when add devices is added/removed/failed or when an
array is started or reshaped.  None of those happen often enough that an
extra spin-up is really going to be an issue.

It is more an issue of simplicity and elegance.  I don't think a sysfs option
is appropriate for that.

But thanks for the suggestion.

NeilBrown