所以我的 NAS（mdraid level5）主板坏了，我建立了一个新系统 - 在那里我重新组装了 raid 并开始重建：
md0 : active raid5 sde4[3] sdc4[0] sdd4[2] sdb4[4]
8634123072 blocks level 5, 64k chunk, algorithm 2 [4/3] [U_UU]
[>....................] recovery = 4.2% (121889248/2878041024) finish=394.4min speed=116448K/sec
几个小时后，我返回，重建失败并出现一些 IO 错误。我重新启动系统并尝试再次重新组装 - 但所有驱动器现在都是备用的：
root@el-kisto:~# mdadm --assemble /dev/md0 /dev/sd[b-e]4 --verbose
mdadm: looking for devices for /dev/md0
mdadm: /dev/sdb4 is identified as a member of /dev/md0, slot 5.
mdadm: /dev/sdc4 is identified as a member of /dev/md0, slot 0.
mdadm: /dev/sdd4 is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sde4 is identified as a member of /dev/md0, slot 3.
mdadm: added /dev/sdc4 to /dev/md0 as 0 (possibly out of date)
mdadm: no uptodate device for slot 1 of /dev/md0
mdadm: added /dev/sde4 to /dev/md0 as 3
mdadm: added /dev/sdb4 to /dev/md0 as 5
mdadm: added /dev/sdd4 to /dev/md0 as 2
mdadm: /dev/md0 assembled from 2 drives and 1 spare - not enough to start the array.
root@el-kisto:~# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : inactive sdb4[5](S) sdc4[0](S) sdd4[2](S) sde4[3](S)
11512164096 blocks
使用 mdadm 检查会产生以下结果：
mdadm --examine /dev/sd[bcde]4 | egrep 'dev|Update|Role|State|Chunk Size|Events'
/dev/sdb4:
Update Time : Mon Aug 28 02:05:59 2023
State : clean
Events : 2045534
Chunk Size : 64K
Number Major Minor RaidDevice State
this 5 8 20 5 spare /dev/sdb4
2 2 8 52 2 active sync /dev/sdd4
3 3 8 68 3 active sync /dev/sde4
4 4 8 36 4 faulty /dev/sdc4
/dev/sdc4:
Update Time : Mon Aug 28 01:54:48 2023
State : clean
Events : 2045530
Chunk Size : 64K
Number Major Minor RaidDevice State
this 0 8 36 0 active sync /dev/sdc4
0 0 8 36 0 active sync /dev/sdc4
2 2 8 52 2 active sync /dev/sdd4
3 3 8 68 3 active sync /dev/sde4
4 4 8 20 4 spare /dev/sdb4
/dev/sdd4:
Update Time : Mon Aug 28 02:05:59 2023
State : clean
Events : 2045534
Chunk Size : 64K
Number Major Minor RaidDevice State
this 2 8 52 2 active sync /dev/sdd4
2 2 8 52 2 active sync /dev/sdd4
3 3 8 68 3 active sync /dev/sde4
4 4 8 36 4 faulty /dev/sdc4
/dev/sde4:
Update Time : Mon Aug 28 02:05:59 2023
State : clean
Events : 2045534
Chunk Size : 64K
Number Major Minor RaidDevice State
this 3 8 68 3 active sync /dev/sde4
2 2 8 52 2 active sync /dev/sdd4
3 3 8 68 3 active sync /dev/sde4
4 4 8 36 4 faulty /dev/sdc4
这看起来还不错，3/4 磁盘的事件计数器是相同的，后面的那个无论如何都是重建的。但不知何故，md 似乎确实认为现在应该有 5 个设备？罪魁祸首似乎是 sdb4，它自我识别为备用和#5，而它应该是活动的和#4？ --组装过程中用力没有帮助。我如何说服 md 将 sd[bde]4 作为降级的 4 磁盘 arry 接收？