磁盘阵列-RAID1

        RAID1是将一个两块硬盘所构成RAID磁盘阵列，其容量仅等于一块硬盘的容量，因为另一块只是当作数据“镜像”。RAID1通过磁盘数据镜像实现数据冗余，在成对的独立磁盘上产生互为备份的数据。当原始数据繁忙时，可直接从镜像拷贝中读取数据，因此RAID1可以提高读取性能，下面是操作方法安排。

1.建立RAID1至少需要两块磁盘。

1.添加磁盘[root@localhost dev]# blkid/dev/sda1: UUID="594f1893-d32b-48d6-88d9-83032584eeb3" TYPE="xfs"/dev/sda2: UUID="a9ccc925-f46d-453a-a11d-72b52cc75355" TYPE="swap" PTTYPE="dos"/dev/sda3: UUID="eddbe0b6-358c-4ac4-8681-008948ed9c73" TYPE="xfs"2.创建相同格式磁盘分区[root@localhost dev]# fdisk /dev/sdcWelcome 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.
Device does not contain a recognized partition tableBuilding a new DOS disklabel with disk identifier 0x23f3010b.
Command (m for help): p
Disk /dev/sdc: 1073 MB, 1073741824 bytes, 2097152 sectorsUnits = sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk label type: dosDisk identifier: 0x23f3010b
   Device Boot      Start         End      Blocks   Id  System
Command (m for help): nPartition type:   p   primary (0 primary, 0 extended, 4 free)   e   extendedSelect (default p): pPartition number (1-4, default 1):First sector (2048-2097151, default 2048):Using default value 2048Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151):Using default value 2097151Partition 1 of type Linux and of size 1023 MiB is set
Command (m for help): tSelected partition 1Hex code (type L to list all codes): fdChanged type of partition 'Linux' to 'Linux raid autodetect'Command (m for help): p
Disk /dev/sdc: 1073 MB, 1073741824 bytes, 2097152 sectorsUnits = sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk label type: dosDisk identifier: 0x9d695fd1
   Device Boot      Start         End      Blocks   Id  System/dev/sdc1            2048     2097151     1047552   fd  Linux raid autodetect

Command (m for help): w

2. mdadm创建RAID1

选项：-C 专用选项：-l 级别 -n 设备个数 -a {yes|no} 自动为其创建设备文件 -c 指定数据块大小（chunk） -x 指定空闲盘（热备磁盘）个数，空闲盘（热备磁盘）能在工作盘损坏后自动顶替 注意：创建阵列时，阵列所需磁盘数为-n参数和-x参数的个数和[root@localhost dev]# cat /partitioncat: /partition: No such file or directory[root@localhost dev]# cat partitioncat: partition: No such file or directory[root@localhost dev]#  mdadm -C /dev/md1 -a yes  -l 1 -n 2 /dev/sd{b,c}mdadm: /dev/sdb appears to be part of a raid array:       level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969mdadm: partition table exists on /dev/sdb but will be lost or       meaningless after creating arraymdadm: Note: this array has metadata at the start and    may not be suitable as a boot device.  If you plan to    store '/boot' on this device please ensure that    your boot-loader understands md/v1.x metadata, or use    --metadata=0.90mdadm: /dev/sdc appears to be part of a raid array:       level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969mdadm: partition table exists on /dev/sdc but will be lost or       meaningless after creating arrayContinue creating array? ymdadm: Defaulting to version 1.2 metadatamdadm: array /dev/md1 started.格式化为xfs[root@localhost mnt]# mkfs.xfs /dev/md1meta-data=/dev/md1               isize=512    agcount=4, agsize=65472 blks         =                       sectsz=512   attr=2, projid32bit=1         =                       crc=1        finobt=0, sparse=0data     =                       bsize=4096   blocks=261888, imaxpct=25         =                       sunit=0      swidth=0 blksnaming   =version 2              bsize=4096   ascii-ci=0 ftype=1log      =internal log           bsize=4096   blocks=855, version=2         =                       sectsz=512   sunit=0 blks, lazy-count=1realtime =none                   extsz=4096   blocks=0, rtextents=0文件系统管理：  重新创建文件系统会损坏原有的文件  创建文件系统  mkfs:    -t   文件系统    创建的磁盘    mkfs.xfs -f /dev/磁盘首先先查看系统的适合格式    cat /proc/filesystems[root@localhost mnt]# mount -o rw /dev/md1 /mnt/md1挂载：    挂载：将新的系统关联到新的系统----如果挂载点原有文件将会被隐藏（解除挂载后显示）  mount  用法：mount  设备  挂载点    -a:表示挂载/etc/fstab 所有文件系统  -n ：默认情况下，mount命令挂载时会写入设备信息，使用这个选项将不会被写入/etc/mtab  -t fstable：指定挂载文件系统类型，默认会调用blkid获取文件系统类型  -r：只读挂载  -w:读写挂载  -o:指定额外的挂载权限  -noexec      :挂载时禁止里面的二进制文件自动运行。  -nosuid :不允许获得管理权限  卸载：解除关联  umount    用法：mount   挂载点或者设备  注意事项：挂载点没有被进程使用  当无法卸载的时候  fuser   --验证或者查看该文件正在被使用    -v:查看文件上正在运行的进程    -mk:杀死正在使用的所有进程查看是否挂载[root@localhost mnt]# mount |grep md1/dev/md1 on /mnt/md1 type xfs (rw,relatime,seclabel,attr2,inode64,noquota)

3.查看创建的RAID1

[root@localhost md1]# mdadm -D  /dev/md1/dev/md1:        Version : 1.2  Creation Time : Thu Jan 20 23:55:34 2022     Raid Level : raid1     Array Size : 1047552 (1023.00 MiB 1072.69 MB)  Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)   Raid Devices : 2  Total Devices : 2    Persistence : Superblock is persistent
    Update Time : Fri Jan 21 19:43:39 2022          State : clean Active Devices : 2Working Devices : 2 Failed Devices : 0  Spare Devices : 0
           Name : localhost.localdomain:1  (local to host localhost.localdomain)           UUID : 1ead9519:d85d9376:4dec83a6:754470a6         Events : 17
    Number   Major   Minor   RaidDevice State       0       8       16        0      active sync   /dev/sdb       1       8       32        1      active sync   /dev/sdc