On Sun, 30 May 2010 23:11:17 -0500 "Leslie Rhorer" <lrhorer@xxxxxxxxxxx> wrote: > > On Sun, 30 May 2010 18:29:16 -0500 > > "Leslie Rhorer" <lrhorer@xxxxxxxxxxx> wrote: > > > > > > > > Am I confused about reshaping a RAID5 to RAID6 array, or is there an > > > error in the man page? The distro I have on one of my servers - Debian > > > "Squeeze" - employs mdadm 3.0.3, internally dated Oct. 22, 2009. The > > man > > > page that comes with the software specifically says: > > > > > > -l, --level= > > > > > > <snip> > > > > > > Not yet supported with --grow. > > > > Man page is wrong. Thanks for reporting. Fixed in current .git and will > > be > > in next release. > > Oh, you're welcome. Thanks to you for all the great work. > > > The syntax for changing levels is simply: > > > > mdadm --grow /dev/mdX --level=6 > > > > This will preserve the number of data disks. If you want to change that > > (or > > anything else) at the same time, you can: > > > > mdadm --grow /dev/mdX --level=6 --raid-disk=8 --chunk-size=1024 -- > > layout=left-asymetric > > I'm a little fuzzy on how the number of member disks can be > maintained while adding additional redundancy. Must the file system(s) be > shrunk so that the total amount of free space on all the members is greater > than the member size? In my situation, that won't work. First of all, I am > using XFS, and I don't think XFS will allow shrinking of the file system. > In any case, however, the file system, which fills the entire array which in > turn uses the entire (unpartitioned) space of each member, is over 93% full. > It's an 8 x 1.5T disk RAID5 array with one spare drive. Or does the --grow > command automatically create a RAID6 array with one missing member? Should > I remove the spare before issuing the command? If so, should I add it along > with the command, something like: > > mdadm --grow /dev/md0 --level6 --raid-disk=9 --add /dev/sdi > > Or will mdadm automagically write the additional information to the 9th > spare / member disk without me doing anything? I didn't say that the number of "member disks" is preserved, but the number of "data disks". Normally you would have a RAID5 with a spare when you convert to RAID6 so the spare gets incorporated. This is the most efficient approach. But if you don't have a spare it will still work. Just tell mdadm what you want and it will do it, or report that it cannot. NeilBrown -- 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
