On Wed, Dec 30, 2009 at 3:25 PM, Kristleifur Daðason <kristleifur@xxxxxxxxx> wrote: > On Wed, Dec 23, 2009 at 11:54 PM, Neil Brown <neilb@xxxxxxx> wrote: >> On Wed, 23 Dec 2009 23:28:37 +0000 >> Kristleifur Daðason <kristleifur@xxxxxxxxx> wrote: >> >>> On Wed, Dec 23, 2009 at 10:45 PM, Neil Brown <neilb@xxxxxxx> wrote: >>> > On Wed, 23 Dec 2009 13:52:54 +0000 >>> > Kristleifur Daðason <kristleifur@xxxxxxxxx> wrote: >>> > >>> >> Hi, >>> >> >>> >> I'm running a raid0 array over a couple of raid6 arrays. I had planned >>> >> 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=0 --raid-devices=2 --metadata=1.1 >>> --chunksize=256 /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 metadata >> and the start of the data for a bitmap - even for raid0 which cannot have >> a bitmap. The 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. If it is different, we >> will have to hack mdadm to allow you to set the data offset manually. > > ... I believe I am guaranteed an identical bitmap size and hence an identical 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" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
