注：本次操作以RHEL4為例，但應該可以應用到其它大部分的distro上（guess）。
目錄
1 mdadm的幾個常用參數
2 創建軟raid的大體流程
3 示例：創建軟raid5（+hotspare）
4 出現故障後的恢復
5 misc
[編輯]mdadm的幾個常用參數
-C 創建Raid，後面跟參數，代表raid設備的名稱。比如：/dev/md0，/dev/md1。
-n 用於創建磁盤陣列的磁盤個數。
-l Raid的級別。
-x 指定用於hotspare（熱備盤）的磁盤個數。如果陣列中有一塊硬盤壞了，它會立刻頂上，並rebuild；
-D 顯示軟raid的詳細信息；
-s 掃描配置文件（/etc/mdadm.conf）或'/proc/mdstat'來查看遺漏的信息f；
[編輯]創建軟raid的大體流程
使用fdisk工具為新磁盤創建分區；
使用mkfs.XXXX工具將剛才劃分好的分區格式化成某種格式的文件系統。比如：ext3，reiserfs等；
使用mdadm來創建軟raid；
創建/etc/mdadm.conf文件（注意文件的格式，包括是否有逗號等等。該文件是為了系統在重啟後能夠自動啟用軟raid。可以查看/etc/rc.sysinit腳本，搜索'mdadm'字符串就明白了）；
[編輯]示例：創建軟raid5（+hotspare）
以下是我的一次實際操作的完整過程：
這是用'fdisk -l'命令查看到的我當前的磁盤和分區情況（只有/dev/sda在使用，其它四個都是新磁盤，沒有分區，沒有格式化）：
# fdisk -lDisk /dev/sda: 6442 MB, 6442450944 bytes255 heads, 63 sectors/track, 783 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System/dev/sda1 * 1 720 5783368+ 83 Linux/dev/sda2 721 783 506047+ 82 Linux swapDisk /dev/sdb: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytesDisk /dev/sdb doesn't contain a valid partition tableDisk /dev/sdc: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytesDisk /dev/sdc doesn't contain a valid partition tableDisk /dev/sdd: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytesDisk /dev/sdd doesn't contain a valid partition tableDisk /dev/sde: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytesDisk /dev/sde doesn't contain a valid partition table
使用fdisk創建分區（本例中將整塊磁盤劃分為一個主分區。其余幾塊磁盤也做相同的操作。）：
# fdisk /dev/sdbDevice contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabelBuilding a new DOS disklabel. Changes will remain in memory only,until you decide to write them. After that, of course, the previouscontent won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)Command (m for help): nCommand action e extended p primary partition (1-4)pPartition number (1-4): 1First cylinder (1-204, default 1):Using default value 1Last cylinder or +size or +sizeM or +sizeK (1-204, default 204):Using default value 204Command (m for help): wThe partition table has been altered!Calling ioctl() to re-read partition table.Syncing disks.
為剛才新建的分區建立文件系統（其余幾個分區依次做相同的操作）：
# mkfs.ext3 /dev/sdb1mke2fs 1.35 (28-Feb-2004)Filesystem label=OS type: LinuxBlock size=1024 (log=0)Fragment size=1024 (log=0)52416 inodes, 208880 blocks10444 blocks (5.00%) reserved for the super userFirst data block=1Maximum filesystem blocks=6737100826 block groups8192 blocks per group, 8192 fragments per group2016 inodes per groupSuperblock backups stored on blocks: 8193, 24577, 40961, 57345, 73729, 204801Writing inode tables: doneCreating journal (4096 blocks): doneWriting superblocks and filesystem accounting information: doneThis filesystem will be automatically checked every 37 mounts or180 days, whichever comes first. Use tune2fs -c or -i to override.
所有磁盤都操作完後，再次用'fdisk -l'查看磁盤及分區狀態：
# fdisk -lDisk /dev/sda: 6442 MB, 6442450944 bytes255 heads, 63 sectors/track, 783 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System/dev/sda1 * 1 720 5783368+ 83 Linux/dev/sda2 721 783 506047+ 82 Linux swapDisk /dev/sdb: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytes Device Boot Start End Blocks Id System/dev/sdb1 1 204 208880 83 LinuxDisk /dev/sdc: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytes Device Boot Start End Blocks Id System/dev/sdc1 1 204 208880 83 LinuxDisk /dev/sdd: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytes Device Boot Start End Blocks Id System/dev/sdd1 1 204 208880 83 LinuxDisk /dev/sde: 214 MB, 214748160 bytes64 heads, 32 sectors/track, 204 cylindersUnits = cylinders of 2048 * 512 = 1048576 bytes Device Boot Start End Blocks Id System/dev/sde1 1 204 208880 83 Linux
使用mdadm創建一個軟raid，raid級別：5；並有一個hotspare盤：
# mdadm -C /dev/md0 -l5 -n3 -x1 /dev/sd[b-e]1mdadm: array /dev/md0 started.
輸出信息顯示軟raid(/dev/md0)已經啟用了。使用mdadm的-D參數（--detail）可以查看軟raid狀態：
# mdadm -D /dev/md0/dev/md0: Version : 00.90.01 Creation Time : Wed Aug 23 15:10:19 2006 Raid Level : raid5 Array Size : 417536 (407.75 MiB 427.56 MB) Device Size : 208768 (203.88 MiB 213.78 MB) Raid Devices : 3 Total Devices : 4Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Wed Aug 23 15:10:21 2006 State : clean Active Devices : 3Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 64K 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 -1 spare /dev/sde1 UUID : f8283de5:39c73d89:b9fbc266:fdceb416 Events : 0.2
生成配置文件（/etc/mdadm.conf）：
# mdadm -D -s >/etc/mdadm.conf
