Volume group considerations

[Kenrick Sy]

Hi,

What are the reasons of extending volume group?

Thanks.

Kenrick

[Antonio Cardoso_1]

Hi
this operation is performed for example to add mirror devices or extend volume group capacity.

Have a look at §6 "Administering a System:
Managing Disks and Files" on http://docs.hp.com/en/B2355-90950/B2355-90950.pdf

[Muthukumar_5]

To allocate additional physical volume to get more disk space. Read vgextend man page for good documentation.

--
Muthu

[Sivakumar TS]

Hi,

Volume groups are extended by adding one or more physical volumes (disks)

After the physical volumes have been successfully added to the volume
group, the disk space they contain can be allocated to logical
volumes. The LVs can be existing and you can increase the SIZE or you can create new LVs also.

Regards,

Siva.

[Kenrick Sy]

Thanks for all your reply.

What are the reasons of configuring additional volume group?

Regards,

Kenrick

[Devender Khatana]

Hi,

Configuring multiple volume groups provides you ease of administration. You can have seperate VGs for different applications or for different type of data within one application itself.

A major advantage also will be if there is some difficult times and you need to restore backup, then restoring a small VG will be fast as compared to the large ones.

HTH,
Devender

[Andrew Rutter]

hi,

it all depends upon the system requirements.

it could be you need specific vg's/lvol's for certain apps or databases.

you may just want an easier way for adding more disk space.

it could be for easier disk and file management

it could also be to make backups easier, specifying just one vg, rather than all vg's

Many reasons, but depends upon what you want to achieve.

if you want to learn more read the links already provided on disk and file management.

Andy

[Senthil Kumar .A_1]

Hi,

One of the most important factor is in Cluster environment. One of the attribute of the Cluster package is it's VG. We tend to create one VG per package. In doing so, the package switch can be independent of other packages. If the packages would have shared the same VG, it becomes inevitable that all the packages sharing the same VG, be switched simultaneosly. So in clustered environment, it is more flexible having multiple VG's, one dedicated to each package.

Regards,
Senthil Kumar .A

[Subramaniyan.S · Accepted solution]

Hi,

VG - LVM can achieve four important advantages over raw physical partitions:

01. Logical volumes can be resized while they are mounted and accessible by the database or file system.

02. Data from one (potentially faulty or damaged) physical device may be relocated to another device that is newer, faster or more resilient, while the original volume remains online and accessible

03. Logical volumes can be constructed by aggregating physical devices to increase performance (via disk striping) or redundancy (via disk mirroring and I/O multipathing)

04. Logical volume snapshots can be created to represent the exact state of the volume at a certain point-in-time, allowing accurate backups to proceed simultaneously with regular system operation

rgds,

Subbu.

[Patrice Le Guyader]

hello,

Look at this thread :

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=993422

my small contibution should be according to backup, when you want to optimize the access on tape. We have seen that on an application like Legato networker it's better to backup 10 lvols of 16 Go than a big one of 160 Go. You can then do parallel writing on drives and save a lot of time..

Regards
Pat

[khilari]

Well, in plain words u extend a volume group to get more space.
U add another disk to ur volume group and then u keep on adding them as u want more disk space.
Ur volume group first spans on some disks, then u want to mirror them in a disk array using xp512. So, the volume group is what disks belong to, they are referred to not by their names but by their volume group name. Like c1t2d9 and c1t2d7 belong to volume group vg02. And thats just the beginning of the story........