服务器软RAID和LVM的实现(2)

例子4：实现raid5
[root@nginx ~]# mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sd{b,c,d,e}
mdadm: /dev/sdb appears to contain an ext2fs file system
  size=2097152K  mtime=Wed Dec 31 16:00:00 1969
mdadm: /dev/sdc appears to contain an ext2fs file system
  size=2097152K  mtime=Wed Dec 31 16:00:00 1969
mdadm: /dev/sdd appears to contain an ext2fs file system
  size=2097152K  mtime=Wed Dec 31 16:00:00 1969
mdadm: /dev/sde appears to contain an ext2fs file system
  size=2097152K  mtime=Wed Dec 31 16:00:00 1969
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.

# watch "cat /proc/mdstat"
Every 2.0s: cat /proc/mdstat                  Tue Nov 15 15:41:46 2011

Personalities : [raid0] [raid1] [raid6] [raid5] [raid4]
md0 : active raid5 sda9[3] sda8[1] sda7[0]
    4016000 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
    [=====>...............]  recovery = 26.2% (527572/2008000) finish
=1.4min speed=17018K/sec

等待完成

模拟raid5原始设备出故障，然后手工移出故障设备，用好的设备替换它

[root@nginx ~]# mdadm /dev/md0 --fail /dev/sdc
mdadm: set /dev/sdc faulty in /dev/md0

[root@nginx ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sde[4] sdd[2] sdc[1](F) sdb[0]
    6286848 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [U_UU]

unused devices: <none>

里面的数据依然可以访问

移走故障设备：
[root@nginx ~]# mdadm /dev/md0 --remove /dev/sdc
mdadm: hot removed /dev/sdc

[root@nginx ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sde[4] sdd[2] sdb[0]
    6286848 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [U_UU]

unused devices: <none

用新设备替换回去进行数据恢复

[root@nginx ~]#  mdadm /dev/md0 --add /dev/sdc
mdadm: added /dev/sdc
[root@nginx ~]#  watch "cat /proc/mdstat" 
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sde[4] sdd[2] sdc[1] sdb[0]
    6286848 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

lvm

pv 物理卷带有逻辑卷元数据的物理设备：分区、硬盘、镜像文件、raid设备等

vg 卷组由多个物理卷组成，容量是所有物理卷的累计，提供容量的存储池

lv 逻辑卷真正操作的对象，对它进行格式化、挂载

盘碟硬盘分区

pv\/lv
vg
pv/\lv

动态调整容量、条带化、镜像、快照

例子1：创建逻辑卷

1、pv
# pvcreate /dev/sda7 /dev/sda8

# pvs
 PV        VG  Fmt  Attr PSize PFree
 /dev/sda7      lvm2 --  1.92G 1.92G
 /dev/sda8      lvm2 --  1.92G 1.92G

# pvdisplay
2、vg
# vgcreate mysql-vg /dev/sda7
 Volume group "mysql-vg" successfully created

# vgs
 VG      #PV #LV #SN Attr  VSize VFree
 mysql-vg  1  0  0 wz--n- 1.91G 1.91G

# vgdisplay

# vgextend mysql-vg /dev/sda8  《－－－增加pv到vg中，进行扩容
 Volume group "mysql-vg" successfully extended

# vgs
 VG      #PV #LV #SN Attr  VSize VFree
 mysql-vg  2  0  0 wz--n- 3.83G 3.83G

3、lv
# lvcreate -n mysql-lv -L 1G mysql-vg
 Logical volume "mysql-lv" created

# lvs
 LV      VG      Attr  LSize Origin Snap%  Move Log Copy%  Convert
 mysql-lv mysql-vg -wi-a- 1.00G

# lvdisplay

# ll /dev/mysql-vg/mysql-lv
lrwxrwxrwx 1 root root 31 11-15 16:27 /dev/mysql-vg/mysql-lv -> /dev/mapper/mysql--vg-mysql--lv

# mkfs.ext3 /dev/mysql-vg/mysql-lv

例子2：如何在线调整lv的容量
一. 增加容量
#vgcreate mysql-vg /dev/sda7
#lvcreate -n mysql-lv -L 1G mysql-vg
#mkfs.ext3 /dev/mysql-vg/mysql-lv
# mount /dev/mysql-vg/mysql-lv  /mnt
# lvextend -L 2G /dev/mysql-vg/mysql-lv  《－－－逻辑卷是正在挂载使用
# resize2fs /dev/mysql-vg/mysql-lv

# df -h
文件系统              容量  已用 可用 已用% 挂载点
/dev/sda2              39G  27G  11G  73% /
/dev/sda1            190M  169M  12M  94% /boot
tmpfs                1009M    0 1009M  0% /dev/shm
/dev/sda5              94G  61G  29G  68% /vmware
/dev/sda6              46G  23G  21G  53% /soft
/dev/mapper/mysql--vg-mysql--lv
                    2.0G  34M  1.9G  2% /mnt