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Old 06-14-2007, 12:13 PM   #1
IanGrant
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Registered: Dec 2006
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RAID with LVM and EVMS empty after dead disk


Hi,

I have (had) a 3 disk RAID array, which was managed with EVMS and used LVM2 for partitioning. After a power cut, it was damaged (not physically though, but EVMS wouldn't bring it up). I tried removing and re-adding the dirty disk, but it wouldn't work. I tried reassembling the array with mdadm, but I got errors about no superblock on sda1. I tried re-creating the arrey with mdadm, and it worked, synced up, but when it came back online, EVMS could not mount the partitions from the LVM volume. They appear to have no filesystem on them. Which means I missing a lot of data
Should I try to create a filesystem, or will that overwrite any data I might be able to recover with a recovery firm or something.

Any suggestions would be *very* welcome!
 
Old 06-14-2007, 08:40 PM   #2
3point2
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Registered: Jan 2006
Distribution: Slackware 11.0
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Creating a filesystem will definitely delete any data in the partition you create it on!

When you say you re-created the array, do you mean you did something like this?

Code:
# mdadm --create /dev/mdX --level=N --raid-devices=N /dev/hdX /dev/hdX ...
I'm reasonably sure that doing this would have destroyed any data on the /dev/hdX partitions! Didn't mdadm give you a warning that raid superblocks were found on any of the partitions?

On the other hand, if you used the --build option to initially create (and now re-create) the array, then mdadm shouldn't have overwritten any data.
 
Old 06-15-2007, 04:30 AM   #3
IanGrant
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Registered: Dec 2006
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Quote:
Originally Posted by 3point2
Creating a filesystem will definitely delete any data in the partition you create it on!

When you say you re-created the array, do you mean you did something like this?

Code:
# mdadm --create /dev/mdX --level=N --raid-devices=N /dev/hdX /dev/hdX ...
I'm reasonably sure that doing this would have destroyed any data on the /dev/hdX partitions! Didn't mdadm give you a warning that raid superblocks were found on any of the partitions?

On the other hand, if you used the --build option to initially create (and now re-create) the array, then mdadm shouldn't have overwritten any data.
Yes, I did exactly that. It said sdb1 and sdc1 (but not sda1, the one that died) already belong to existing arrays, but I went ahead... going on examples/advice elsewhere

I'm screwed then?
 
Old 06-15-2007, 06:13 PM   #4
3point2
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Registered: Jan 2006
Distribution: Slackware 11.0
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Sorry but I'm afraid it looks that way. Using --create initialises a RAID array for the first time, erasing all data. That's why mdadm warns you if any of the partitions involved look like they belong to an existing array. The correct option would have been --assemble, possibly leaving out any partitions you knew were bad and then adding --run to force it to run the array as degraded.

Unless anyone else knows better, I would say it looks like you're starting from scratch... Ouch
 
  


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