情報

よくまとまってる、、感謝。
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$ cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 nvme1n1p3[1] nvme0n1p3[0]
      498975744 blocks super 1.2 [2/2] [UU]
      bitmap: 0/4 pages [0KB], 65536KB chunk

$ sudo mdadm --detail --scan
ARRAY /dev/md/0 metadata=1.2 name=鯖:0 UUID=鯖UUID
$ sudo mdadm --detail /dev/md0
/dev/md0:
           Version : 1.2
     Creation Time : Thu Dec 20 20:13:10 2018
        Raid Level : raid1
        Array Size : 498975744 (475.86 GiB 510.95 GB)
     Used Dev Size : 498975744 (475.86 GiB 510.95 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Fri Dec 21 09:03:10 2018
             State : clean
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : bitmap

              Name : 鯖名:0  (local to host 鯖名)
              UUID : 鯖UUID
            Events : 1873

    Number   Major   Minor   RaidDevice State
       0     259        4        0      active sync   /dev/nvme0n1p3
       1     259        7        1      active sync   /dev/nvme1n1p3

• bitmapに関して

  0/8 means that no memory is being used for the in-memory bitmap cache.