* RAID 0 -> 1 possible?
@ 2004-03-11 20:44 Jeff Hoffmann
2004-03-11 23:03 ` Maarten van den Berg
2004-03-12 5:53 ` Clemens Schwaighofer
0 siblings, 2 replies; 6+ messages in thread
From: Jeff Hoffmann @ 2004-03-11 20:44 UTC (permalink / raw)
To: linux-raid
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: RAID 0 -> 1 possible?
2004-03-11 20:44 RAID 0 -> 1 possible? Jeff Hoffmann
@ 2004-03-11 23:03 ` Maarten van den Berg
2004-03-12 5:53 ` Clemens Schwaighofer
1 sibling, 0 replies; 6+ messages in thread
From: Maarten van den Berg @ 2004-03-11 23:03 UTC (permalink / raw)
To: linux-raid
On Thursday 11 March 2004 21:44, Jeff Hoffmann wrote:
> Hello list,
>
> Is it possible to convert from RAID 0 to 1 without data loss?
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'...
> 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
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.
> Any RAID-mojo-masters with the answer?
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: RAID 0 -> 1 possible?
2004-03-11 20:44 RAID 0 -> 1 possible? Jeff Hoffmann
2004-03-11 23:03 ` Maarten van den Berg
@ 2004-03-12 5:53 ` Clemens Schwaighofer
2004-03-12 14:44 ` Jeff Hoffmann
1 sibling, 1 reply; 6+ messages in thread
From: Clemens Schwaighofer @ 2004-03-12 5:53 UTC (permalink / raw)
To: Jeff Hoffmann; +Cc: linux-raid
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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
==========================================================
Tequila Japan, 6-17-2 Ginza Chuo-ku, Tokyo 104-8167, JAPAN
Tel: +81-(0)3-3545-7703 Fax: +81-(0)3-3545-7343
http://www.tequila.jp
==========================================================
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: RAID 0 -> 1 possible?
2004-03-12 5:53 ` Clemens Schwaighofer
@ 2004-03-12 14:44 ` Jeff Hoffmann
2004-03-12 15:28 ` Paul Clements
0 siblings, 1 reply; 6+ messages in thread
From: Jeff Hoffmann @ 2004-03-12 14:44 UTC (permalink / raw)
To: Clemens Schwaighofer; +Cc: linux-raid
On 03/12/04 00:53, Clemens Schwaighofer wrote:
> | 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.
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: RAID 0 -> 1 possible?
2004-03-12 14:44 ` Jeff Hoffmann
@ 2004-03-12 15:28 ` Paul Clements
2004-03-12 19:31 ` Jeff Hoffmann
0 siblings, 1 reply; 6+ messages in thread
From: Paul Clements @ 2004-03-12 15:28 UTC (permalink / raw)
To: Jeff Hoffmann; +Cc: linux-raid
Jeff Hoffmann wrote:
> > | Convert / from RAID 0 to 1 without requiring a backup/reinstall/restore
> > | scenario
> Indeed. In my case, the data actually on the partition is < 25%.
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: RAID 0 -> 1 possible?
2004-03-12 15:28 ` Paul Clements
@ 2004-03-12 19:31 ` Jeff Hoffmann
0 siblings, 0 replies; 6+ messages in thread
From: Jeff Hoffmann @ 2004-03-12 19:31 UTC (permalink / raw)
To: Paul Clements; +Cc: linux-raid
On 03/12/04 10:28, Paul Clements wrote:
> 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...
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
^ permalink raw reply [flat|nested] 6+ messages in thread
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2004-03-11 20:44 RAID 0 -> 1 possible? Jeff Hoffmann
2004-03-11 23:03 ` Maarten van den Berg
2004-03-12 5:53 ` Clemens Schwaighofer
2004-03-12 14:44 ` Jeff Hoffmann
2004-03-12 15:28 ` Paul Clements
2004-03-12 19:31 ` Jeff Hoffmann
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