Re: rebuilding raided root partition

[Emanoil Kotsev <deloptes@yahoo.com>]

Miles Fidelman wrote:

> Hi Folks,
> 
> I've been busily recovering from a bad crash (strangely enough, a single
> disk drive failure that brought down an entire raided environment, with
> spares).
> 
> I've pretty much recovered and rebuilt everything, EXCEPT....
> 
> my root partition is raided, and is now running only on its single spare
> drive:
> 
> -----
> server1:~# more /proc/mdstat
> md2 : inactive sdd3[0] sdb3[2]
>       195318016 blocks
> 
> server1:~# mdadm --detail /dev/md2  [details omitted]
> /dev/md2:
>      Raid Level : raid1
>     Device Size : 97659008 (93.13 GiB 100.00 GB)
>    Raid Devices : 2
>   Total Devices : 2
> Preferred Minor : 2
>     Persistence : Superblock is persistent
> 
>          State : active, degraded
>  Active Devices : 0
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 2
> 
>     Number   Major   Minor   RaidDevice State
>        0       8       51        0      spare rebuilding   /dev/sdd3
>        1       0        0        -      removed
> 
>        2       8       19        -      spare   /dev/sdb3
> ------
> 
> note the line "spare rebuilding" - that's the result of: mdadm --add
> /dev/md2 /dev/sdd3
> unfortunately, it doesn't seem to really be doing anything - it's been
> saying "rebuilding" for several hours
> 
> now for another mirror device, doing an mdadm --add, kicked off a resync
> (as indicated by cat /proc/mdstat) that concluded just fine with a
> rebuilt mirror array
> 
> but for this array, it just shows "active, degraged, and rebuilding" in
> mdadm --detail, and "inactive" in /proc/mdstat
> 
> about the only difference I can see, is that the array that rebuilt
> started with one primary drive, to which I added a 2nd drive, and then a
> spare; the one that's hanging is running on a spare, and it thinks I'm
> adding another spare  (note: both serve as physical volumes underlying
> LVM)
> 
> so..... on to questions:
> 
> 1. What's going on?
> 
> 2. Any suggestions on how to reassemble the array?  mdadm --assemble
> /dev/md2 tells me I need to deactivate the device, but then, it's my /
> volume - which leaves me a little stumped
> 
> Thanks very much,
> 
> Miles Fidelman
> 
> 
> 
> 
> 

You may try using the --run option.

I do following

1) start the array with the healthy partition
        let's say md0 with sda1 sdb1
        and sdb1 is faulty

mdadm -A /dev/md0 --add /dev/sda1 --run

2) add the faulty partition to the array for syncing

mdadm /dev/md0 --add /dev/sdb1 

3) check /proc/mdstat

cat /proc/mdstat

you can also stop the array at any time

mdadm -S /dev/md0

hope it helps 

regards