From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: raid5 to raid6 - reshape very slow Date: Tue, 29 May 2012 10:56:19 +1000 Message-ID: <20120529105619.4dd15511@notabene.brown> References: <4FC41970.5080009@infinitedepth.com.au> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/R95JdjpxOIB/rnvnBG7NT1r"; protocol="application/pgp-signature" Return-path: In-Reply-To: <4FC41970.5080009@infinitedepth.com.au> Sender: linux-raid-owner@vger.kernel.org To: Jonathan Molyneux Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/R95JdjpxOIB/rnvnBG7NT1r Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 29 May 2012 10:33:52 +1000 Jonathan Molyneux wrote: > Hi Everyone, >=20 > I'm currently reshaping my raid5 array into a raid6 array (by adding a=20 > spare and growing). >=20 > Unfortunately I didn't research the nuances before doing so and missed=20 > the opportunity to --layout=3Dpreserve. >=20 > As a result the array is rebuilding by use of a backup-file, at a rather= =20 > slow pace. >=20 > md1 : active raid6 sde1[0] sdb1[6] sdh1[5] sdc1[4] sdg1[3] sdd1[2] sdf1[1] > 7325679680 blocks super 0.91 level 6, 64k chunk, algorithm 18=20 > [7/6] [UUUUUU_] > [=3D=3D=3D=3D=3D=3D=3D=3D=3D>...........] reshape =3D 47.0% (6894= 13888/1465135936)=20 > finish=3D4126.9min speed=3D3132K/sec >=20 > I have tried the following so far: >=20 > * read ahead tweaking > * stripe_cache_size tweaking (not a limiting factor - mdadm seems to=20 > tune this appropriately) > * running the backup file from dev/shm (only for testing purposes) >=20 > The reshape does not seem to be IO or CPU bound, it just seems to be=20 > limited by the sync's and meta data updates to each disk. >=20 > Is it possible to increase the buffer/stripes that mdadm process in a=20 > batch to speed up the process (~41m/2 -> 1G) ? >=20 > Any thoughts would be appreciated (even to confirm there is nothing to=20 > be done). The only thing to do is to wait. This is very much a seek-bound operation and there is little room for making it go faster. In a few months we might see the need for the backup file disappear, which will improve things somewhat, but it will still be slowish. NeilBrown --Sig_/R95JdjpxOIB/rnvnBG7NT1r Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT8Qesznsnt1WYoG5AQLOVhAAjoF8XFROpz+/IA+w0ja/NfddBdPEUwCz TMTrOfRXSZBK0vQ99TRnzvRD2fFhg4TTPlpidoz3575FVo6YUhH0dkqOKTGEHSZC sy/ZuMUCBdU9Wb5k67PedD6PcObtXgW6EyqZaS6LOBh62AoyupXx+ohheVU6BLVR bg5YS+9NSqS8TloFzosqy/4k3WNdxDKl0QsTebjU5zmpIb7GrmUo2hNIy6jywOEX RB5HUfuwEomT5RkKovW5DMojVld8c1CWtLNb/778on2Ss0gBQcXD8/kJszWF3AqN 150swoMtdvKxeyxCKi8gxyZq2rN62NPIDLHBVHxA1IgpfnkXRO/MNXENel0iWkMR Zq7LWrWgOLyyUcnfdVgH1ZyEkbIXLdyv25FJHuGfkm+K+8A92s/UXZVRwWSmwQ1e zgvCvYpkY+juxKDSQfLy+VyA0XRAxH+ROHyrvPwMn3HqcFFoIc3DTnINLcNHaUxa 7zSX495LXbjg+1jMhLfEvEyE55crJ+bYd64sIOFUAGUvjcDinEPsTbYXPLSlBqCw z6U03b3m24y41sUaNXbGWmgd1AN4NRsIA/T36Eo7UKmk7y2GZkowuHr6lV0//9+l ztASTr2YIifNmA1Ah8LY3Ous6eCwKK3gO4EbkXXMSjkBrnIFK8JDGXnTzfuNWi+o drkCiQ21boI= =YH8i -----END PGP SIGNATURE----- --Sig_/R95JdjpxOIB/rnvnBG7NT1r--