RAID 0 -> 1 possible?

Hello list,

Is it possible to convert from RAID 0 to 1 without data loss?

Given a system with two disks, three partitions on each: boot, /, and swap.

Convert / from RAID 0 to 1 without requiring a backup/reinstall/restore scenario

Any RAID-mojo-masters with the answer?

TIA,

Jeff Hoffmann

No, obviously. Raid 1 is mirrored, so your useable space is only half of your total capacity at best. Raid 0 uses the full capacity of the disks, so until you can solve how to put twice as many data onto the same space, one cannot convert from raid0 -> raid1 without 'losing data'...

Even without the <total data size> problems as outlined above, you cannot touch either disks of a raid 0 set without destroying data, that is the whole point of raid 0. So, even an online-migration tool sounds implaudible.

I'm not a RAID-mojo-master, but then again I don't believe one needs to be one to answer this. It stems directly from the theory of operation of the levels.

Maarten

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Jeff Hoffmann wrote:

| Hello list,
|
| Is it possible to convert from RAID 0 to 1 without data loss?
|
| Given a system with two disks, three partitions on each: boot, /, and
swap.
|
| Convert / from RAID 0 to 1 without requiring a backup/reinstall/restore
| scenario
|
| Any RAID-mojo-masters with the answer?

I think that can't work unless you add two more disks. Raid 0 is strip where 1 is mirroring.

- --
Clemens Schwaighofer - IT Engineer & System Administration
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http://www.tequila.jp
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Indeed. In my case, the data actually on the partition is < 25%. Perhaps there's a way to shrink the RAID 0 set? That would allow a new partition (not striped) to be created to store the data.

Thanks for your input,

Jeff Hoffmann

Well, in that case you just might be able to do it. You'll need to shrink your filesystem (if you have one) ala resize2fs or similar. Then raidreconf the raid0. Then edit the partition table (there are tools to help with this, or just use fdisk very carefully) to shrink the partition. Then you can create a new partition and dump the data there. Create another similarly sized partition and raid1 them together...

It's certainly possible...but it's starting to sound like a backup/restore might be easier than all that (you probably want to backup before doing these types of things anyway, if you care about the data).

--
Paul

That seems like it would work, but I thought raidreconf was used for adding disks to arrays, not making them smaller. How do you use raidreconf in this manner?

Thanks for your help,

Jeff Hoffmann