From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Hill Subject: Re: implications of partitioning and raid Date: Thu, 5 Jan 2012 16:12:17 +0000 Message-ID: <20120105161217.GA23196@cthulhu.home.robinhill.me.uk> References: <1325778034.4777.44.camel@hermosa.lnx.copansys.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="/04w6evG8XlLl3ft" Return-path: Content-Disposition: inline In-Reply-To: <1325778034.4777.44.camel@hermosa.lnx.copansys.com> Sender: linux-raid-owner@vger.kernel.org To: "Peter W. Morreale" Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids --/04w6evG8XlLl3ft Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu Jan 05, 2012 at 08:40:34AM -0700, Peter W. Morreale wrote: >=20 > I'm wondering what the implications are for having multiple raid sets on > a partitioned disk wrt to disk failures.=20 >=20 > For example, suppose I create two partitions on a set of disks and > create raid sets on those partitions. Further, not all raid sets > reference the same disks. IOW, md0 references disks 1 and 2, and md1 > references disk 1 and 3. (overly simplistic for discussion purposes) >=20 > Assume a portion of disk 1 goes 'bad' (localized within one of those > partitions), is noticed by md and a rebuild is warranted. =20 >=20 > What is the behavior? =20 >=20 Any failure will only affect the single array member where the error occurred. In most cases this is due to a catastrophic disk failure though, so will also occur on other partitions of the disk (and the arrays using them) as well. > Will both raid sets start a rebuild? Or only the affected raid set? >=20 > IOW, would there be two rebuild tasks, one for each raid set? Or a > single rebuild that encompasses all raid sets (within the same raid > level, of course) on the disk in question?=20 >=20 Rebuild processes are per raid set, but only one rebuild will be done at a time using the same disk (so if disk 1 fails and is replaced, then there's separate rebuilds pending for md0 and md1, but only one will run at a time). > What I am getting at is whether there would be any advantage to > partitioning disks for failure purposes. =20 >=20 There's an advantage in being able to prioritise the rebuilds (so I can rebuild the array containing / before that containing /opt for example) and there's some cases where there's a transient failure (a write error causes the array member to be failed, but testing shows up no errors) in which case it reduces the rebuild time as only a single array needs to be rebuilt. The latter is pretty rare though, unless you have other underlying problems (such as power issues or poor quality I/O chipsets/drivers). HTH, Robin --=20 ___ =20 ( ' } | Robin Hill | / / ) | Little Jim says .... | // !! | "He fallen in de water !!" | --/04w6evG8XlLl3ft Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (GNU/Linux) iEYEARECAAYFAk8Fy+AACgkQShxCyD40xBIY4ACfXtbHO1TdBlu6+1ohbBUbqeZ2 e7wAn2pS7s1d4JALhE6DYLmbCS0weW4l =OCKq -----END PGP SIGNATURE----- --/04w6evG8XlLl3ft--