Messages in this thread | | | From | Kyle Moffett <> | Subject | Re: [PATCH 000 of 5] md: Introduction | Date | Sun, 22 Jan 2006 20:54:04 -0500 |
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On Jan 22, 2006, at 20:25, Neil Brown wrote: > Changing the size of the devices is a separate operation that has > been supported for a while. For each device in turn, you fail it > and replace it with a larger device. (This means the array runs > degraded for a while, which isn't ideal and might be fixed one day). > > Once all the devices in the array are of the desired size, you run > mdadm --grow /dev/mdX --size=max > and the array (raid1, raid5, raid6) will use up all available space > on the devices, and a resync will start to make sure that extra > space is in-sync.
One option I can think of that would make it much safer would be to originally set up your RAID like this:
md3 (RAID-5) __________/ | \__________ / | \ md0 (RAID-1) md1 (RAID-1) md2 (RAID-1)
Each of md0-2 would only have a single drive, and therefore provide no redundancy. When you wanted to grow the RAID-5, you would first add a new larger disk to each of md0-md2 and trigger each resync. Once that is complete, remove the old drives from md0-2 and run: mdadm --grow /dev/md0 --size=max mdadm --grow /dev/md1 --size=max mdadm --grow /dev/md2 --size=max
Then once all that has completed, run: mdadm --grow /dev/md3 --size=max
This will enlarge the top-level array. If you have LVM on the top- level, you can allocate new LVs, resize existing ones, etc.
With the newly added code, you could also add new drives dynamically by creating a /dev/md4 out of the single drive, and adding that as a new member of /dev/md3.
Cheers, Kyle Moffett
-- I lost interest in "blade servers" when I found they didn't throw knives at people who weren't supposed to be in your machine room. -- Anthony de Boer
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