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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