On Thu, May 14, 2009 at 02:06:59PM -0700, Tyler MacDonald wrote: > Got an answer: RTFM! :-) > > -z, --size= > [...] > This value can be set with --grow for RAID level 1/4/5/6. If the > array was created with a size smaller than the currently active > drives, the extra space can be accessed using --grow. The size > can be given as max which means to choose the largest size that > fits on all current drives. > > > > > Tyler MacDonald <tyler@yi.org> wrote: > > Hello debian! > > > > I have a RAID-5 mdadm array with 4x500GB drives (1.4TB usable). I'm > > running out of space and am going to buy a new drive, but I would like to > > move to 1TB drives (either RAID-5 or RAID-10, haven't quite decided yet). I > > can't afford to buy all new 1TB drives at once so I'm thinking about just > > adding a fifth drive to the array now, and then upgrading the remaining > > drives as I can afford it. > > > > I've dug around trying to find information on how to do this and haven't > > seen anything yet. I've imagined the process to be something like: ("Plan > > A") > > > > 1. One-by-one, replace the 500GB drives with 1TB drives, rebuilding the > > array using only the first 500GB of each drive. > > > > 2. Once all drives are 1TB, do something to tell mdadm to reshape the > > array so that the full 1TB from each drive is used > > > > 3. e2fsck -f /dev/md0 && resize2fs /dev/md0 > > > > Does step #2 exist? If so, how is it done? > > > > If that's not possible, I'm considering the following plan: ("Plan B") > > > > 1. Buy 2x1TB drives, set them up as RAID-5 (1TB usable) > > > > 2. Copy 1TB of the 1.4TB to the new array > > > > 3. Degrade my existing 4x500GB array, freeing up 1x500GB drive > > > > 4. Copy the remaining 400GB to the "spare" drive > > > > 5. Tear down the 3x500GB array > > > > 6. Set up 2x500GB from the old array as a 1TB RAID-0 stripe > > > > 7. Add the 2x500GB RAID-0 to the new RAID-5 as a "1TB drive", > > making the new array have 2TB capacity, eg; > > mdadm --add /dev/md0 /dev/md1 > > mdadm --grow /dev/md0 ... > > > > 8. Copy the data from the "spare" drive over to the new array > > > > 9. Repeat step #7 with the remaining 2x500GB drives, resulting in > > 3TB capacity on the array > > > > I'd really prefer to go with "Plan A". It's cheaper to get started with, > > far less complicated, and doesn't risk data loss during the move. > > > > Any ideas? Is this possible? I wouldn't make up raid devices with other raid device (I think its possible), but I seem to remember thats its not advisable. the first option would be my preference ( I have done it previously), I have taken a 3 drive 500Gb and replaced it slowly with 1TB drives, take out drive, let it rebuild and then replace another drive let it rebuild, till I have 3x1T but still using the same space as before, then use the grow as you suggested above, you can also grow to go from 3 drives to 4 drives. I would suggest though, when you get to around 5 or 6 drives you look at raid6 instead. > > > > Thanks, > > Tyler > > > > -- "Keep good relations with the Greecians." - George W. Bush 04/09/1999 as quoted in The Economist
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