[olug] Software RAID / accidentally raidhotadd to wrong md

[Terry]

Wow, paste your raidtab if you don't mind....let me
take a peek at that then read your stuff below.  That
will help....

--- lug at robotz.com wrote:
> Issue summary:  Had problems with 1 of a 3 drive
> software raid array.
> Harddrive is not physically bad, but the array
> failed today on boot.
> Used “raidhotadd” to get all of the raid5 partitions
> (md0 – md3) 
> up and running with the exception of the most
> important partition 
> (md4).
> 
> I accidentally tried to “raidhotadd” 2 of the 3
> drives from md4 into 
> md2.  Now hdb2 and hdc2 think they are part of md2
> when they actually 
> should be part of md4.  This is not reflected in
> /etc/raidtab but 
> must be stored somewhere I cannot find.
> (superblock?)
> 
> This leaves only 1 drive in md4 and therefore md4
> will not start 
> even degraded.  md4 is a RAID 5 partition, which is
> supposed to include 
> hda2, hdb2, and hdc2.  Since RAID wont start on md4,
> I cannot simply 
> use “raidhotremove” and “raidhotadd” to correct this
> mistake (assuming 
> that would correct the mistake).
> 
> I used “raidsetfaulty” to deactivate hdb2 to stop
> interfering with 
> the start of md2.  (because hdb2 belongs in md4 and
> raidhotremove 
> refuses to get hdb2 out of md2 without deactivating
> the partition)
> 
> lsraid reports md0 – md3 correctly.  However, typing
> “lsraid –A –d 
> /dev/hdb2” or “lsraid –A –d /dev/hdc2” shows them as
> a member of 
> md2 still.  They should be in md4 instead.
> 
> My question #1:  Did my mistake hose the data in
> both hdb2 and hdc2 
> making it impossible to recover md4 (my most
> critical partition containing 
> /home) or is hdb2 and hdc2 merely confused about
> where they belong 
> but still within them is my critical data making
> recovery of md4 
> possible?
> 
> My question #2: If recovery is possible, should I
> then “mkraid /dev/md4 
> –f” and hope for the best or is there a safer way to
> _save_ my data? 
> Or perhaps there is a way to make hdb2 and hdc2
> realize again that 
> they are part of md4.   
> 
> Keep in mind that since md4 won’t start I can’t
> reverse the mistake 
> with raidhotadd.
> 
> If I failed to provide any details please let me
> know and I will 
> elaborate further.
> 
> Thank you.
> 
> 
> 
> 
> 
> 
> 
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=====
Terry

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