From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Hill Subject: Re: about raid5 recovery when created Date: Tue, 8 Dec 2009 13:14:46 +0000 Message-ID: <20091208131446.GA21130@cthulhu.home.robinhill.me.uk> References: <389deec70912080501u6c6bc90ei2d34ef245a1dae9e@mail.gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="bp/iNruPH9dso1Pn" Return-path: Content-Disposition: inline In-Reply-To: <389deec70912080501u6c6bc90ei2d34ef245a1dae9e@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid List-Id: linux-raid.ids --bp/iNruPH9dso1Pn Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue Dec 08, 2009 at 09:01:23PM +0800, hank peng wrote: > Hi, all: > As we know, when a raid5 array is created, recovery will be going on > which involves some read, one xor and one write. Since there is no > real data in the disk at the time, besides, if I am willing to wait > for recovery to complete and then use this raid5, how about adding > support for a fast recovery method? Right now, what is in my mind is > zero all disks which belong to this raid5. I think it will increase > raid5 recovery speed when created and decrease CPU usage, since all > zero is also XORed. > What do raid developers think? >=20 It'll decrease CPU usage but increase I/O - you're now needing to write to all disks. Most systems will be I/O limited rather than CPU limited, so the current approach works better. If you want to zero the disks then do this before creating the array - you can then use --assume-clean to skip the resync process. Cheers, Robin --=20 ___ =20 ( ' } | Robin Hill | / / ) | Little Jim says .... | // !! | "He fallen in de water !!" | --bp/iNruPH9dso1Pn Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (GNU/Linux) iEYEARECAAYFAkseUUYACgkQShxCyD40xBLkkACdF7wSHUyFTBjmHGyHTwUEDB6X DAUAn1+UlhxaAbJIjZ2vnSTOQDZcWC1s =HLwd -----END PGP SIGNATURE----- --bp/iNruPH9dso1Pn--