From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Kristleifur_Da=F0ason?= Subject: Re: raid0 not growable? Date: Wed, 30 Dec 2009 17:55:38 +0000 Message-ID: <73e903670912300955o63e5adb2va33a610f27ab1edb@mail.gmail.com> References: <73e903670912230552n226e9052q182174cba32f3c54@mail.gmail.com> <20091224094557.1ae96a0d@notabene> <73e903670912231528u6d3cd2ekd0fa4ade06adbcf5@mail.gmail.com> <20091224105424.62c41b25@notabene> <73e903670912300725g20dc1746mf51db90a7e90e929@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <73e903670912300725g20dc1746mf51db90a7e90e929@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: linux-raid List-Id: linux-raid.ids On Wed, Dec 30, 2009 at 3:25 PM, Kristleifur Da=F0ason wrote: > On Wed, Dec 23, 2009 at 11:54 PM, Neil Brown wrote: >> On Wed, 23 Dec 2009 23:28:37 +0000 >> Kristleifur Da=F0ason wrote: >> >>> On Wed, Dec 23, 2009 at 10:45 PM, Neil Brown wrote: >>> > On Wed, 23 Dec 2009 13:52:54 +0000 >>> > Kristleifur Da=F0ason wrote: >>> > >>> >> Hi, >>> >> >>> >> I'm running a raid0 array over a couple of raid6 arrays. I had p= lanned >>> >> on growing the arrays in time, and now turns out to be the time. >>> >> >>> > If the two raid6 arrays are exactly the same size, then you >>> > could grow the two raid6 arrays, create a new raid0 over them >>> > with the same block size and all your data will still be there. >>> > But if they are not the same size, that won't work. >>> >>> Current chunksize is 256 and metadata is 1.1. So it's just a "mdadm >>> --create /dev/md_bigraid0 --level=3D0 --raid-devices=3D2 --metadata= =3D1.1 >>> --chunksize=3D256 /dev/md_raid6a /dev/md_raid6b", right? >> >> Yes... there is a possible complication though. >> With 1.1 metadata mdadm reserves some space between the end of the m= etadata >> and the start of the data for a bitmap - even for raid0 which cannot= have >> a bitmap. =A0The amount of space reserved is affected by the size of= the >> devices. >> So it is possible that the "data offset" will be different. >> You should check the data offset before and after. =A0If it is diffe= rent, we >> will have to hack mdadm to allow you to set the data offset manually= =2E > > ... I believe I am guaranteed an identical bitmap size and hence an i= dentical data offset. > > And in theory, this case is closed. Thank you, all. > Yep, it worked great. We built the new raid0 array over the old one, and did a "fsck.jfs -n" dry-run over the filesystem. Still there, clean as a whistle. Next was a quick "mount -o remount,resize /tank" which grew the JFS filesystem in a second or two. Very quick and painless. For my purposes, I consider raid0 arrays to be growable. Such was the ease. Even though raid0 may not be officially growable. -- Kristleifur -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html