Linux磁碟對映DM

nmon中看到磁碟如dm-0..dm-4。如果分割槽時使用了LVM，則一般生成dm-N邏輯卷。它類似於普通分割槽的一個分割槽sda0。只不過它利用了Mapper Device機制，在Physical Volume上虛擬出來的分割槽資訊。

檢視對映關係

[root@hpcentos1 ~]# cd /dev/mapper; ll
total 0
crw-rw---- 1 root root 10, 58 Dec 27 10:32 control
lrwxrwxrwx 1 root root      7 Dec 27 10:32 vg_hpcentos1-LogVol03 -> ../dm-4
lrwxrwxrwx 1 root root      7 Dec 27 10:32 vg_hpcentos1-LogVol04 -> ../dm-3
lrwxrwxrwx 1 root root      7 Dec 27 10:32 vg_hpcentos1-LogVol05 -> ../dm-2
lrwxrwxrwx 1 root root      7 Dec 27 10:32 vg_hpcentos1-lv_root  -> ../dm-0
lrwxrwxrwx 1 root root      7 Dec 27 10:32 vg_hpcentos1-lv_swap  -> ../dm-1

檢視DM上的檔案系統

[root@hpcentos1 mapper]# df -h
Filesystem                             Size  Used  Avail  Use%  Mounted on
/dev/mapper/vg_hpcentos1-lv_root        50G  3.0G   44G     7%  /       
tmpfs                                   48G  336K   48G     1%  /dev/shm
/dev/sda1                              485M   37M  424M     8%  /boot
/dev/mapper/vg_hpcentos1-LogVol03      193G   12G  171G     7%  /home
/dev/mapper/vg_hpcentos1-LogVol04      1.6T  901G  651G    59%  /opt
/dev/mapper/vg_hpcentos1-LogVol05       45G  6.8G   36G    16%  /usr

檢視磁碟分割槽與LVM

[root@hpcentos1 mapper]# fdisk -l

Disk /dev/sda: 3000.5 GB, 3000513552384 bytes
255 heads, 63 sectors/track, 364791 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 262144 bytes / 786432 bytes
Disk identifier: 0x0000b2de

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512256   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64      267350  2146970112   8e  Linux LVM

從上面可以看出，sda2就是lvm對應的分割槽