Linux Raid - mdadm

說明

mdadm - Linux Software Raid

主要套件：mdadm
主要服務：mdmonitor (監控 Raid 狀態)

新增 Raid

Raid 0

# mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc

Raid 1

# mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc --spare-devices=/dev/sdd

Raid 5

# mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --spare-devices=/dev/sde

使用 Raid

# mkfs.ext4 /dev/md0
# mkdir /data01
# mount /dev/md0 /data01

維護 Raid

Raid 設定檔 /etc/mdadm.conf

重新掃描 raid 與更新設定檔
mdadm --verbose --detail -scan > /etc/mdadm.conf 

 顯示 Raid 整體狀態

cat /proc/mdstat

顯示 /dev/md0 詳細資訊

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Mon Nov  3 06:03:03 2014
     Raid Level : linear
     Array Size : 4194288 (4.00 GiB 4.29 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Mon Nov  3 06:03:03 2014
          State : clean 
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

       Rounding : 0K

           Name : localhost.localdomain:0  (local to host localhost.localdomain)
           UUID : a50ac9f2:62646d92:725255bd:7f9d30e3
         Events : 0

    Number   Major   Minor   RaidDevice State
       0       8       16        0      active sync   /dev/sdb
       1       8       32        1      active sync   /dev/sdc

監控 Raid 狀態

/proc/mdstat

# awk '/^md/ {printf "%s: ", $1}; /blocks/ {print $NF}' </proc/mdstat
md126: [UU]
md127: [UUUUU]

# watch -t 'cat /proc/mdstat'

iotop 檢視狀態

# iotop -a -p $(sed 's, , -p ,g' <<<`pgrep "_raid|_resync|jbd2"`)

iostat 檢視狀態

# iostat -dmy 1 /dev/md127
# iostat -dmy 1 /dev/md126 

移除 Raid

停止並永久移除

# mdadm --stop /dev/md0
# mdadm --remove /dev/md0

啟動 raid

# mdadm --asemble /dev/md0

NOTE : The assemble command reads the /etc/mdadm.conf file to start the array. In case you did not save your configuration in mdadm.conf before stopping the array, this command would fail. You can use the below command to recreate the mdadm.conf file :
# mdadm –examine –scan > /etc/mdadm.conf

延伸閱讀

• http://thegeekdiary.com/redhat-cento...id-with-mdadm/
• http://xmodulo.com/create-software-r...adm-linux.html
• https://www.cyberciti.biz/faq/centos...-create-raid1/