Naming Convention:
Volume group's name is unique and can have a max. 255 chars.
Default names of the form /dev/vgxx
Few Points to remember :
1. Max VGs per system can be changed thru the kernel tunable 'maxvgs'.
Minimum value is 0
Default Value is 16
Maximum value is 256
This tunable has been removed in version 11.31.
2. A Volume group can contain minimum 1 PV and maximum 255 PVs.
3. A VG can contain maximum 255 LVs.
Here is the list of mostly used commands for managing VG's :
To create a volume group :
# vgcreate
To remove a volume group :
# vgremove
To activate, deactivate, change the chars of a VG :
# vgchange
To modify the config parameters of a VG :
# vgmodify
To backup the VG config details :
# vgcfgbackup
To restore the VG config details from a config file :
# vgcfgrestore
To display the info for all or a particular VG :
# vgdisplay
To export a VG and its associated LVs:
# vgexport
To import a VG into the system as well as adding an existing VG into /etc/lvmtab :
# vgimport
To scan all PV s looking for LVs and VGs :
# vgscan
To add a PV to a VG :
# vgextent
To remove a PV from a VG :
# vgreduce
To sync all the mirrored LVs in a VG :
# vgsync
To modify the VGID on a PV :
# vgchgid
To migrate a VG from legacy to persistent device files :
# vgdsf
Here are few Examples,
1. To create a volume group :
a. Create a directory under /dev,
# mkdir /dev/vg01
b. Create a group device file
# mknod /dev/vg01/group c 64 0xnn0000
where
c -> to mention group is a character device file
64 -> is the major number for the group file. It should be always 64
0xnn0000 -> is the monir number for the group file in hexadecimal and nn is the unique vg number
c. Finally create the vg using a pv
# vgcreate /dev/vgname /dev/disk/disk12
2. To display all the volume groups :
# vgdisplay
3. To display the properties of a volume group :
# vgdisplay vg00
4. To display the detailed properties of a volume group :
# vgdisplay -v vg00
5. To add a PV to a VG :
# vgextend /dev/vg01 /dev/disk/disk13
6. To remove a PV from a VG :
# vgreduce /dev/vg01 /dev/disk/disk13
Before executing this command, make sure the PV disk13 doesnot hold any LV.
Otherwise vgreduce command wont work.
7. To deactivate a VG :
# vgchange -a n vg01
8. To activate a VG :
# vgchange -a y vg01
9. To export a VG :
# vgexport -s -v -m /tmp/vg01.map vg01
where /tmp/vg01.map is the map file whicj will hold PE-LE mappings and other config details.
10. To import a VG :
You need to create the VG dir and the group device file as like in the VG creation process.
Then you can import the VG using the below command,
# vgimport -s -v -N -m /tmp/vg01.map /dev/vg01
11. To change the "Max PV" attribtue to 255 for a VG :
# vgchange -a n vg01
# vgmodify -p 255 -n vg01
# vgchange -a y vg01
12. To change the "Max PE per PV" attribtue to 8128 for a VG :
# vgchange -a n vg01
# vgmodify -e 8128 -n vg01
# vgchange -a y vg01
13. To hold the write operation on a VG for 400 secs :
# vgchange -Q w -t 400 vg01
This operation is called as quiescing a VG.
14. To hold both read and write operation on a VG untill it is explicitly resumed :
# vgchange -Q rw vg01
15. To resume a quiesced VG :
# vgchange -R vg01
16. To rename a VG :
a. Deactivate the VG :
# vgchange -a n vg01
b. Find out the minor number of the Vg's group file :
# ls -l /dev/vg01/group
c. Export the VG :
# vgexport -m /tmp/vg01.map vg01
d. Create the vg dir in the new name and create its group file with the same minor number
# mkdir /dev/dbvg
# mknod /dev/dbvg/group c 64 0x010000
e. Import the VG
# vgimport -m /tmp/vg01.map /dev/dbvg
f. Backup the VG config info :
# vgcfgbackup /dev/dbvg
g. Activate the VG :
# vgchange -a y /dev/dbvg
h. Remove the saved conf information file for the old vg name :
# rm /etc/lvmconf/vg01.conf
i. Modify all the references in other config files like /etc/fstab
very good
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