使用mdadm工具实现软RAID 5实战案例
作者：尹正杰
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一.准备工作
1>.实验环境说明
本次试验我打算采用4个分区设备来做RAID 5，如下图所示。
一般情况下使用3块设备就可以做RAID 5,但我之所以使用4块设备，是想用第4块设备充当空闲硬盘，当RAID 5中某一块设备损坏时，它会立即顶上去。 温馨提示： 由于我们使用的是分区来模拟RAID实战(即软RAID)，因此在分区时务必指定Id类型为"fd"(即"Linux raid auto") 生产环境中我们很少用磁盘分区来做RAID，而是直接使用整块磁盘来做RAID阵列，而且会有专门的磁盘阵列卡。
2>.为/dev/sdb磁盘新增一个200G的分区
[root@yinzhengjie.com ~]# fdisk /dev/sdb Welcome to fdisk (util-linux 2.23.2). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): p Disk /dev/sdb: 644.2 GB, 644245094400 bytes, 1258291200 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x8c3b1f6e Device Boot Start End Blocks Id System /dev/sdb1 2048 209717247 104857600 fd Linux raid autodetect Command (m for help): n Partition type: p primary (1 primary, 0 extended, 3 free) e extended Select (default p): p Partition number (2-4, default 2): First sector (209717248-1258291199, default 209717248): Using default value 209717248 Last sector, +sectors or +size{K,M,G} (209717248-1258291199, default 1258291199): +200G Partition 2 of type Linux and of size 200 GiB is set Command (m for help): p Disk /dev/sdb: 644.2 GB, 644245094400 bytes, 1258291200 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x8c3b1f6e Device Boot Start End Blocks Id System /dev/sdb1 2048 209717247 104857600 fd Linux raid autodetect /dev/sdb2 209717248 629147647 209715200 83 Linux Command (m for help): t Partition number (1,2, default 2): 2 Hex code (type L to list all codes): L 0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris 1 FAT12 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT- 2 XENIX root 39 Plan 9 83 Linux c4 DRDOS/sec (FAT- 3 XENIX usr 3c PartitionMagic 84 OS/2 hidden C: c6 DRDOS/sec (FAT- 4 FAT16 <32M 40 Venix 80286 85 Linux extended c7 Syrinx 5 Extended 41 PPC PReP Boot 86 NTFS volume set da Non-FS data 6 FAT16 42 SFS 87 NTFS volume set db CP/M / CTOS / . 7 HPFS/NTFS/exFAT 4d QNX4.x 88 Linux plaintext de Dell Utility 8 AIX 4e QNX4.x 2nd part 8e Linux LVM df BootIt 9 AIX bootable 4f QNX4.x 3rd part 93 Amoeba e1 DOS access a OS/2 Boot Manag 50 OnTrack DM 94 Amoeba BBT e3 DOS R/O b W95 FAT32 51 OnTrack DM6 Aux 9f BSD/OS e4 SpeedStor c W95 FAT32 (LBA) 52 CP/M a0 IBM Thinkpad hi eb BeOS fs e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD ee GPT f W95 Ext'd (LBA) 54 OnTrackDM6 a6 OpenBSD ef EFI (FAT-12/16/ 10 OPUS 55 EZ-Drive a7 NeXTSTEP f0 Linux/PA-RISC b 11 Hidden FAT12 56 Golden Bow a8 Darwin UFS f1 SpeedStor 12 Compaq diagnost 5c Priam Edisk a9 NetBSD f4 SpeedStor 14 Hidden FAT16 <3 61 SpeedStor ab Darwin boot f2 DOS secondary 16 Hidden FAT16 63 GNU HURD or Sys af HFS / HFS+ fb VMware VMFS 17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fc VMware VMKCORE 18 AST SmartSleep 65 Novell Netware b8 BSDI swap fd Linux raid auto 1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid fe LANstep 1c Hidden W95 FAT3 75 PC/IX be Solaris boot ff BBT 1e Hidden W95 FAT1 80 Old Minix Hex code (type L to list all codes): fd Changed type of partition 'Linux' to 'Linux raid autodetect' Command (m for help): p Disk /dev/sdb: 644.2 GB, 644245094400 bytes, 1258291200 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x8c3b1f6e Device Boot Start End Blocks Id System /dev/sdb1 2048 209717247 104857600 fd Linux raid autodetect /dev/sdb2 209717248 629147647 209715200 fd Linux raid autodetect Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. WARNING: Re-reading the partition table failed with error 16: Device or resource busy. The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8) Syncing disks. [root@yinzhengjie.com ~]#