On 28/03/21 03:14, David T-G wrote:
> Hi, all --
>
> I recently migrated our disk farm to a new box with a new OS build
> (openSuSE from KNOPPIX). Aside from the usual challenges of setting
> up the world again, I have a 3-device RAID5 volume that won't start.
> The other metadevice is fine, though; I think we can say that the md
> system is running. Soooooo ... Where do I start?
>
> diskfarm:~ # cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 sdc1[3] sdd1[4] sdb1[0]
> 11720265216 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [U_UU]
This looks wrong - is this supposed to be a four-drive array? U_UU
implies a missing drive ... as does [4/3]
>
> md127 : inactive sdl2[0](S) sdj2[3](S) sdf2[1](S)
> 2196934199 blocks super 1.2
>
> unused devices: <none>
>
> [No, I don't know why md127 was first a moment ago!] I tried reassembling
> the device, but mdadm doesn't like it.
>
> diskfarm:~ # mdadm --stop /dev/md127
> mdadm: stopped /dev/md127
> diskfarm:~ # mdadm --assemble --scan
> mdadm: /dev/md/750Graid5md assembled from 1 drive - not enough to start the array.
> mdadm: Found some drive for an array that is already active: /dev/md/0
> mdadm: giving up.
> mdadm: No arrays found in config file or automatically
>
> But ... what's with just 1 drive?
>
> diskfarm:~ # for D in /dev/sd[fjl] ; do parted $D print ; done
> Model: ATA WDC WD7500BPKX-7 (scsi)
> Disk /dev/sdf: 750GB
> Sector size (logical/physical): 512B/4096B
> Partition Table: gpt
> Disk Flags:
>
> Number Start End Size File system Name Flags
> 2 1049kB 750GB 750GB ntfs Linux RAID raid
> 3 750GB 750GB 134MB ext3 Linux filesystem
>
> Model: ATA WDC WD7500BPKX-7 (scsi)
> Disk /dev/sdj: 750GB
> Sector size (logical/physical): 512B/4096B
> Partition Table: gpt
> Disk Flags:
>
> Number Start End Size File system Name Flags
> 2 1049kB 750GB 750GB ntfs Linux RAID raid
> 3 750GB 750GB 134MB xfs Linux filesystem
>
> Model: ATA Hitachi HDE72101 (scsi)
> Disk /dev/sdl: 1000GB
> Sector size (logical/physical): 512B/512B
> Partition Table: msdos
> Disk Flags:
>
> Number Start End Size Type File system Flags
> 1 1049kB 4227MB 4226MB primary ntfs diag, type=27
> 2 4227MB 754GB 750GB primary reiserfs raid, type=fd
> 3 754GB 754GB 134MB primary reiserfs type=83
> 4 754GB 1000GB 246GB primary reiserfs type=83
>
> Slice 2 on each is the RAID partition, slice 3 on each is a little
> filesystem for bare-bones info, and slice 4 on sdl is a normal basic
> filesystem for scratch content.
>
> diskfarm:~ # mdadm --examine /dev/sd[fjl]2 | egrep '/dev|Name|Role|State|Checksum|Events|UUID'
> /dev/sdf2:
> Array UUID : 88575f01:592167fd:bd9f9ba1:a61fafc4
> Name : diskfarm:750Graid5md (local to host diskfarm)
> State : clean
> Device UUID : e916fc67:b8b7fc59:51440134:fa431d02
> Checksum : 43f9e7a4 - correct
> Events : 720
> Device Role : Active device 1
> Array State : AAA ('A' == active, '.' == missing, 'R' == replacing)
> /dev/sdj2:
> Array UUID : 88575f01:592167fd:bd9f9ba1:a61fafc4
> Name : diskfarm:750Graid5md (local to host diskfarm)
> State : clean
> Device UUID : 0b847f84:83e80a3d:a0dc11e7:60bffc9f
> Checksum : 9522782b - correct
> Events : 177792
> Device Role : Active device 2
> Array State : A.A ('A' == active, '.' == missing, 'R' == replacing)
> /dev/sdl2:
> Array UUID : 88575f01:592167fd:bd9f9ba1:a61fafc4
> Name : diskfarm:750Graid5md (local to host diskfarm)
> State : clean
> Device UUID : cc53440e:cb9180e4:be4c38d4:88a676eb
> Checksum : fef95256 - correct
> Events : 177794
> Device Role : Active device 0
> Array State : A.. ('A' == active, '.' == missing, 'R' == replacing)
>
> Slice f2 looks great, but slices j2 & l2 seem to be missing -- even though
> they are present. Worse, the Events counter on sdf2 is frighteningly
> small. Where did it go?!? So maybe I consider sdf2 failed and reassemble
> from the other two [only] and then put f2 back in?
Yes I'm afraid so. I'd guess you've been running a failed raid-5 for
ages, and because something hiccuped when you shut it down, the two good
drives drifted apart, and now they won't start ...
>
> Definitely time to stop, take a deep breath, and ask for help :-)
>
Read up about overlays on the web site, use an overlay to force-assemble
the two good drives, run fsck etc to check everything's good (you might
lose a bit of data, hopefully very little), then if everything looks
okay do it for real. Ie force-assemble the two good drives, then re-add
the third. I'd just do a quick smartctl health check on all three drives
first, just to make sure nothing is obviously wrong with them - a
problem could kill your array completely! Then add the third drive back
in (whether you use --add or --re-add probably won't make much difference).
Oh - and fix whatever is wrong with md0, too, before that dies on you!
Cheers,
Wol
