Thank you so far Andreas.
I was able to re-assemble the array with the defective disk (sdd in
this case) and the old spare (sde).
It was rebuilding over night and now it looks like this:
mdadm --detail -v /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Jan 7 18:14:37 2015
Raid Level : raid5
Array Size : 8790405120 (8383.18 GiB 9001.37 GB)
Used Dev Size : 2930135040 (2794.39 GiB 3000.46 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Thu Jan 9 19:37:16 2020
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : bitmap
Name : NAS:0 (local to host NAS)
UUID : 7b0eee59:07f87155:bdad1d0e:6e3cbad6
Events : 280445
Number Major Minor RaidDevice State
4 8 64 0 active sync /dev/sde
1 8 16 1 active sync /dev/sdb
3 8 32 2 active sync /dev/sdc
0 8 48 3 active sync /dev/sdd
I was able to mount the array in read-only and it looks like the data
is fine; i also ran a btrfs check in read-only mode and it found no
errors.
So far so good :)
Although disk sdd is still reporting an increasing read error rate via SMART:
smartctl -a /dev/sdd | grep "Raw_Read_Error_Rate"
1 Raw_Read_Error_Rate 0x002f 200 200 051 Pre-fail
Always - 764
therefore i need to replace this disk in the next days.
Thank you so far for your help.
Am Mi., 8. Jan. 2020 um 13:25 Uhr schrieb Andreas Klauer
<Andreas.Klauer@xxxxxxxxxxxxxx>:
>
> On Wed, Jan 08, 2020 at 10:31:28AM +0100, Marco Heiming wrote:
> > 0 8 0 - spare /dev/sda
>
> Your spare was /dev/sda
>
> > mdadm --examine /dev/sd[b-z]
>
> Here you deliberately examine sdb-z, so what happened to sda?
>
> You mentioned drive letters changed, but is it really not there anymore?
>
> If you don't know which drives you synced in the array then who does...?
>
> Regards
> Andreas Klauer
