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所以，这是历史：断电后，我的 RAID5 无法工作，因为需要重新添加 3 个驱动器。我启动了 mdadm --manage --re-add /dev/md0 /dev/sd[abd]1 ，就像我在电源问题后经常做的那样。

这通常需要 2 秒，但这次运行了很长时间。不幸的是，又发生了一次停电。

当前的 RAID5 不会重新组装：

# mdadm --examine /dev/sd*1
/dev/sda1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x8b
     Array UUID : 0993cb6a:f3459891:b7cdab4b:6ea12dfe
           Name : abydos:0  (local to host abydos)
  Creation Time : Sat Apr 14 16:22:03 2018
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953193984 (931.36 GiB 1000.04 GB)
     Array Size : 2929790976 (2794.07 GiB 3000.11 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
Recovery Offset : 977060096 sectors
   Unused Space : before=262064 sectors, after=0 sectors
          State : clean
    Device UUID : 3c88a981:9bc7d431:d89b5a24:d08f46d8

Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 14 10:50:52 2018
  Bad Block Log : 512 entries available at offset 16 sectors - bad blocks present.
       Checksum : dcd48bf - correct
         Events : 7388

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 0
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdb1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x8b
     Array UUID : 0993cb6a:f3459891:b7cdab4b:6ea12dfe
           Name : abydos:0  (local to host abydos)
  Creation Time : Sat Apr 14 16:22:03 2018
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953193984 (931.36 GiB 1000.04 GB)
     Array Size : 2929790976 (2794.07 GiB 3000.11 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
Recovery Offset : 977060096 sectors
   Unused Space : before=262064 sectors, after=0 sectors
          State : active
    Device UUID : 33272fbd:e6031c19:23768dd1:85a9bb52

Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 14 10:50:52 2018
  Bad Block Log : 512 entries available at offset 16 sectors - bad blocks present.
       Checksum : 58421802 - correct
         Events : 7388

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 1
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 0993cb6a:f3459891:b7cdab4b:6ea12dfe
           Name : abydos:0  (local to host abydos)
  Creation Time : Sat Apr 14 16:22:03 2018
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953260976 (931.39 GiB 1000.07 GB)
     Array Size : 2929790976 (2794.07 GiB 3000.11 GB)
  Used Dev Size : 1953193984 (931.36 GiB 1000.04 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262064 sectors, after=66992 sectors
          State : active
    Device UUID : c2a0569a:bdc4990d:f548e5b6:d909315d

Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 14 10:50:52 2018
  Bad Block Log : 512 entries available at offset 16 sectors
       Checksum : df78c9b4 - correct
         Events : 7388

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 2
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdd1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x8b
     Array UUID : 0993cb6a:f3459891:b7cdab4b:6ea12dfe
           Name : abydos:0  (local to host abydos)
  Creation Time : Sat Apr 14 16:22:03 2018
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953260972 (931.39 GiB 1000.07 GB)
     Array Size : 2929790976 (2794.07 GiB 3000.11 GB)
  Used Dev Size : 1953193984 (931.36 GiB 1000.04 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
Recovery Offset : 977060096 sectors
   Unused Space : before=262064 sectors, after=66988 sectors
          State : active
    Device UUID : e184b5de:6a891977:e3531c58:45698c2f

Internal Bitmap : 8 sectors from superblock
    Update Time : Fri Sep 14 10:50:52 2018
  Bad Block Log : 512 entries available at offset 16 sectors - bad blocks present.
       Checksum : 3b269e62 - correct
         Events : 7388

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 3
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)

虽然一切看起来都不错，但我无法重新组装：

 # mdadm --assemble --verbose --force --run /dev/md0 /dev/sd*1
mdadm: looking for devices for /dev/md0
mdadm: /dev/sda1 is identified as a member of /dev/md0, slot 0.
mdadm: /dev/sdb1 is identified as a member of /dev/md0, slot 1.
mdadm: /dev/sdc1 is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sdd1 is identified as a member of /dev/md0, slot 3.
mdadm: added /dev/sdb1 to /dev/md0 as 1
mdadm: added /dev/sdc1 to /dev/md0 as 2
mdadm: added /dev/sdd1 to /dev/md0 as 3
mdadm: added /dev/sda1 to /dev/md0 as 0
mdadm: failed to RUN_ARRAY /dev/md0: Input/output error
mdadm: Not enough devices to start the array.

# cat /proc/mdstat 
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty] 
md0 : inactive sdd1[3] sdc1[2] sdb1[1] sda1[0]
      3906454958 blocks super 1.2

unused devices: <none>

请注意，没有磁盘被标记为备用。另外，在 dmesg 中，我看到：

[352041.228763] md: md127 stopped.
[352045.333213] md/raid:md127: not clean -- starting background reconstruction
[352045.333246] md/raid:md127: device sdb1 operational as raid disk 2
[352045.333672] md/raid:md127: not enough operational devices (3/4 failed)
[352045.333951] md/raid:md127: failed to run raid set.
[352045.333953] md: pers->run() failed ...

我不明白这里发生了什么，一切看起来都很好（所有磁盘上的更新时间和事件都相同），我不确定如何恢复数据。有任何想法吗 ？没有磁盘是备用的，没有磁盘过期，也没有磁盘出现故障。

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1 回答 1

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我认为答案很简单：RAID 不是防止电源故障的技术；相反，它是一种防止磁盘发生故障的技术（通常一次出现一个（RAID5 情况）或两个（RAID6））。使用写入缓存（在操作系统中，或在驱动器本身中），任何驱动器上都可能存在数据丢失，并且 RAID 软件只会看到太多（在 RAID5 的情况下超过一个）驱动器没有状态他们应该有。

RAID5 想要从剩余的好磁盘重建坏磁盘，但在您的情况下，软件无法检测到足够的好磁盘。

如果幸运的话，mdadm的repair动作可以使 RAID 再次一致，但这并不意味着您没有丢失数据。一旦 RAID 再次处于活动状态，您应该执行完整的文件系统检查。

于 2019-01-27T22:14:27.570 回答