Re: about raid5 recovery when created

[Neil Brown <neilb@suse.de>]

On Wed, 9 Dec 2009 19:34:04 -0800
Michael Evans <mjevans1983@gmail.com> wrote:

> On Wed, Dec 9, 2009 at 5:43 PM, Neil Brown <neilb@suse.de> wrote:
> > On Wed, 9 Dec 2009 19:29:04 +0800
> > hank peng <pengxihan@gmail.com> wrote:
> >
> >> I think it is better to implement this function in kernel's md layer.
> >> I wonder what Neil Brown think of this?
> >
> > I don't think it is worth the effort.
> > You probably would save some CPU time as you don't need to XOR, but as has
> > been said, we are usually IO bound, not CPU bound.
> >
> > With the current arrangement, you can start using the array immediately - you
> > don't have to wait for the initial recovery to complete.
> > If you zeroed all devices at create time, you would have to wait for that to
> > complete before using the array.
> >
> > So I see very little gain, and significant cost.
> >
> > NeilBrown
> >
> >
> 
> When I assemble an array I tend to have checked the devices before
> hand; it would not be difficult to make the final pass a zeroing pass
> if I knew I could vastly speed up post-assembly performance.  As I
> stated, it's merely a lack of clarity in the documentation.

If you would like to create a patch against the man page, I would be happy to
accept it.

NeilBrown