Software RAID

Software RAID †

説明 †

3台の SATA disk を使い RAID5 を組む。
RAID 作成には mdadm (Linux ソフトウェア RAID md デバイスの管理) を使用する。

設定 †

○ RAID の作成
# mdadm -C /dev/md0 -l5 -n3 /dev/sdb /dev/sdc /dev/sdd
# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdd1[2] sdc1[1] sdb1[0]
      1953519872 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>
# mdadm -D /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Sun Nov  9 01:35:02 2008
     Raid Level : raid5
     Array Size : 1953519872 (1863.02 GiB 2000.40 GB)
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 3
  Total Devices : 3
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Mon Nov 24 14:58:10 2008
          State : clean
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : f69d5a71:1bcb82bb:51ee741b:3924c9c3
         Events : 0.2

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       33        1      active sync   /dev/sdc1
       2       8       49        2      active sync   /dev/sdd1


○ RAID 設定の保存
# echo "DEVICE partitions" > /etc/mdadm.conf
# echo "MAILADDR root" >> /etc/mdadm.conf
# mdadm -D --scan >> /etc/mdadm.conf

既存 RAID5(三台構成) にディスクを追加(四台構成)

# mdadm /dev/md0 -a /dev/sde1
# mdadm --misc --detail /dev/md0
/dev/md0:
        Version : 0.90
  Creation Time : Sun Nov  9 01:35:02 2008
     Raid Level : raid5
     Array Size : 1953519872 (1863.02 GiB 2000.40 GB)
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 3
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sat May  1 16:24:09 2010
          State : clean
 Active Devices : 3
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : f69d5a71:1bcb82bb:51ee741b:3924c9c3
         Events : 0.112880

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       33        1      active sync   /dev/sdc1
       2       8       49        2      active sync   /dev/sdd1

       3       8       65        -      spare   /dev/sde1


3台のRAID5に4台目を増設する場合(nは合計台数)
同時に複数台追加も可能.
# mdadm -G /dev/md0 -n 4
mdadm: Need to backup 384K of critical section..
mdadm: ... critical section passed.



# mdadm --misc --detail /dev/md0
/dev/md0:
        Version : 0.91
  Creation Time : Sun Nov  9 01:35:02 2008
     Raid Level : raid5
     Array Size : 1953519872 (1863.02 GiB 2000.40 GB)
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sat May  1 16:28:46 2010
          State : clean, recovering
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

 Reshape Status : 0% complete
  Delta Devices : 1, (3->4)

           UUID : f69d5a71:1bcb82bb:51ee741b:3924c9c3
         Events : 0.113202

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       33        1      active sync   /dev/sdc1
       2       8       49        2      active sync   /dev/sdd1
       3       8       65        3      active sync   /dev/sde1


# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sde1[3] sdd1[2] sdc1[1] sdb1[0]
      1953519872 blocks super 0.91 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
      [>....................]  reshape =  0.1% (1250560/976759936)  finish=1787.8min speed=9092K/sec

unused devices: <none>


速くリビルドする
# echo 800000 > /proc/sys/dev/raid/speed_limit_max
# echo 200000 > /proc/sys/dev/raid/speed_limit_min

コマンド一覧 †

注意点 †

参考資料 †

資料4: mdadm(8) ver.1.5 man page [日本語]