Re: Install failes after md raid replace

[Andrei Borzenkov]

04.01.2016 20:14, Tobias Lang пишет:
> Am 04.01.16 um 17:51 schrieb Andrei Borzenkov:
>> 04.01.2016 12:40, Tobias Lang пишет:
>>> Hi everybody,
>>>
>>> after the replacement of a faulty disk in a md raid setup (Raid 1), we
>>> are not able to update grub.
>>>
>>> The system is an Ubuntu 12.04.5 LTS, with the latests patches installed,
>>> and running Linux version 3.2.0-95-generic (address@hidden).
>>>
>>> Disk replacement procedure involved the following steps:
>>>
>>> # sgdisk -R /dev/sda /dev/sdb
>>> # sgdisk -G /dev/sda
>>> # mdadm /dev/mdX -a /dev/sdbX
>>>
>>
>> Sorry, I do not understand this. I assume /dev/sdb is the current good
>> disk and /dev/sda is replacement disk. In this case you are trying to
>> add disk that already exists in array once more. This is simply not
>> possible.
> 
> The disk showed a failure like this:
> 
> ----------------------------------------------------
> md2 : active raid1 sdb3[1] sda3[0](F)
>       1073740664 blocks super 1.2 [2/1] [_U]
> ----------------------------------------------------
> 
> I removed the disk from the array before replacing it with a new one:
> 
> # mdadm /dev/mdX -r /dev/sdaX
> 
> After that, the array only had one disk (as this is a two disk array).
> 

Again - your array had /dev/sdb3 at this point (because this is the only
non-failed disk). You tried to add /dev/sdb3 again. That makes no sense,
sorry. Apparently some step is missing or incorrectly described.

>>> After resync, this failes:
>>>
>>
>> Resync? I get "/dev/vdb1 busy".
> 
> Of course, the raid has to resync the data to the replaced (and
> currently) empty disk.
> 

You misunderstand. When I execute this command /dev/vdb1 *is* part of
active array; I cannot "add" it again. There is nothing to sync yet.

>> Please show exact steps to reproduce starting with degraded array; and
>> show array state at each step (cat /proc/mdstat and mdadm --detail
>> /dev/mdX).
>>
> 
> The current /proc/mdstat looks like this:
> 

And grub-probe still fails? Do you still have failed disk present in the
system and visible?

> ----------------------------------------------------
> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
> [raid4] [raid10]
> md1 : active raid1 sda2[2] sdb2[1]
>       524276 blocks super 1.2 [2/2] [UU]
> 
> md3 : active raid1 sda4[2] sdb4[1]
>       1822442815 blocks super 1.2 [2/2] [UU]
> 
> md2 : active raid1 sda3[2] sdb3[1]
>       1073740664 blocks super 1.2 [2/2] [UU]
> 
> md0 : active raid1 sda1[2] sdb1[1]
>       33553336 blocks super 1.2 [2/2] [UU]
> 
> unused devices: <none>
> 
> ----------------------------------------------------
> 
> An example 'mdadm --detail /dev/md0' looks like this:
> 

I can produce such example myself. I am interested in steps to reproduce
this problem.

> ----------------------------------------------------
> /dev/md0:
>         Version : 1.2
>   Creation Time : Fri Apr 19 10:11:20 2013
>      Raid Level : raid1
>      Array Size : 33553336 (32.00 GiB 34.36 GB)
>   Used Dev Size : 33553336 (32.00 GiB 34.36 GB)
>    Raid Devices : 2
>   Total Devices : 2
>     Persistence : Superblock is persistent
> 
>     Update Time : Sat Jan  2 22:25:50 2016
>           State : clean
>  Active Devices : 2
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 0
> 
>            Name : rescue:0
>            UUID : 72974d0d:40970c9e:83dfc291:dd07bfba
>          Events : 162
> 
>     Number   Major   Minor   RaidDevice State
>        2       8        1        0      active sync   /dev/sda1
>        1       8       17        1      active sync   /dev/sdb1
> 
> ----------------------------------------------------
> 
> Best regards
> 
> Tobi
>