From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: [Lsf-pc] [LSF/MM TOPIC] a few storage topics
Date: Wed, 25 Jan 2012 11:23:52 +1100
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Cc: Jan Kara <jack@suse.cz>, "Darrick J. Wong" <djwong@us.ibm.com>,
	Mike Snitzer <snitzer@redhat.com>,
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To: Boaz Harrosh <bharrosh@panasas.com>
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On Thu, 19 Jan 2012 01:42:12 +0200 Boaz Harrosh <bharrosh@panasas.com> wrot=
e:


> >> Or possibly modify md-raid5 not to snapshot dirty pages prior to xor/w=
rite?
> >> (I never really bothered to find out if it really does this.)
>=20
> md-raid5/1 currently copies all pages if that what you meant.
>=20

Small correction:  RAID5 and RAID6 copy all pages.
                   RAID1 and RAID10 do not.

If the incoming bios had nicely aligned pages which were somehow flagged to
say that they would not change until the request completed, then it should =
be
trivial to avoid that copy.

NeilBrown


> >   Not sure either. Neil should know :) (added to CC).
> >=20
> > 								Honze
>=20
> Thanks
> Boaz


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