lvm on linux

jack_zheng

to create:
1. fdisk sdc, sdd, sde, set file type to 8e.
/dev/sdc1               1          62      497983+  8e  Linux LVM
/dev/sdc2              63         130      546210   8e  Linux LVM
2. create physical volume
[email=root@vm]root@vm[/email]
:~# pvcreate /dev/sdc1 /dev/sdc2 /dev/sdd1 /dev/sde1
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdc2" successfully created
  Physical volume "/dev/sdd1" successfully created
  Physical volume "/dev/sde1" successfully created
[email=root@vm]root@vm[/email]
:~# pvscan
  No matching physical volumes found
3.create volume group.
[email=root@vm]root@vm[/email]
:~# vgcreate test /dev/sdc1 /dev/sdc2 /dev/sdd1 /dev/sde1
  Volume group "test" successfully created
[email=root@vm]root@vm[/email]
:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               test
  PV Size               484.00 MB / not usable 0   
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              121
  Free PE               121
  Allocated PE          0
  PV UUID               7VkY0C-ENAP-aJgM-c3Ft-J7dK-SJBL-Mbf4hQ
...

4.create logical volume
[email=root@vm]root@vm[/email]
:~# lvcreate -L 50m -n test_lv1 test
  Rounding up size to full physical extent 52.00 MB
  Logical volume "test_lv1" created
[email=root@vm]root@vm[/email]
:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/test/test_lv1
  VG Name                test
  LV UUID                CsQqLG-Qsyp-TDUb-Fdv1-Hpgx-irRm-NjT8XT
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                52.00 MB
  Current LE             13
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           254:4

5. make file system on lvm
[email=root@vm]root@vm[/email]
:~# mke2fs /dev/test/test_lv1
[email=root@vm]root@vm[/email]
:~# mount /dev/test/test_lv1 /mnt/
6. management
  pvmove, ext2resize, lvextend...

7. remove
[email=root@vm]root@vm[/email]
:~# umount /dev/test/test_lv1
[email=root@vm]root@vm[/email]
:~# lvremove /dev/test/test_lv1
Do you really want to remove active logical volume "test_lv1"? [y/n]: y
  Logical volume "test_lv1" successfully removed
[email=root@vm]root@vm[/email]
:~# vgremove test
  Volume group "test" successfully removed
[email=root@vm]root@vm[/email]
:~# pvscan
  PV /dev/sdc1         lvm2 [486.31 MB]
  PV /dev/sdc2         lvm2 [533.41 MB]
  PV /dev/sdd1         lvm2 [2.00 GB]
  PV /dev/sde1         lvm2 [4.00 GB]
  Total: 4 [6.99 GB] / in use: 0 [0   ] / in no VG: 4 [6.99 GB]
[email=root@vm]root@vm[/email]
:~# lvdisplay
[email=root@vm]root@vm[/email]
:~# vgdisplay
[email=root@vm]root@vm[/email]
:~# pvdisplay
  --- NEW Physical volume ---
  PV Name               /dev/sdc1
  VG Name               
  PV Size               486.31 MB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               7VkY0C-ENAP-aJgM-c3Ft-J7dK-SJBL-Mbf4hQ
...

8. code
1) kernel. in linux/driver/md/, there are several parts.
- md. for multi disk and volume management.
- dm-. device mapper, it is the interface for system calls.
- dm-crypt. for block encryption.
2) user space.
- device-mapper.1.02.19 is the library to communicate with the kernel for lvm and other applications.
- LVM2.2.02.25.

9. reference
http://sources.redhat.com/dm/
http://www.chinaunix.net/jh/4/72921.html



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