Volume Group In AIX – A Primer

Volume Group is at the highest level in LVM hierarchy. Hard disks are used as Physical Volumes in LVM. Then Physical partitions are mapped to Logical Partitions. Logical Partitions are combined to Logical Volumes. These Logical Volumes comprise the Volume Group. For more information you can see the previous article: Aix Logical Volume Manager A Brief Introduction.

The Volume Groups are totally logical entities. And a number of operations can be carried out on Volume Groups.

Below are the Volume Group characteristics.

Naming of Volume Group: The name of Volume Group should be unique and the name should range from 1 to 15 characters.

States of Volume Group: The following states are possible for Volume Group:

1. Active/Complete.
2. Active/Partial.
3. Inactive.

Active/Complete State
The active/complete state of Volume Group signifies that all of the physical volumes in the Volume Group are fully active. In this state the Volume Group is fully usable by the applications. The varyonvg command is used to bring the Volume Group to active/complete state.

Active/Partial State
The active/partial state of Volume Group signifies that all of the physical volumes in the Volume Group are not active. Some of the PVs can be in unavailable or removed state. This may cause the alarming condition and the data loss may happen if continuing in this state.

Inactive State
The inactive state of Volume Group signifies that the Volume Group is not in use and can’t be used for any application. The varyoffvg command used to bring down the Volume Group.

Access Permissions For Volume Group
The Volume Group can be varied on with two types of permissions:

1. Read-only.
2. Read-write.

Type of Volume Group
The Volume Groups are of three type:

1. Normal Volume Group.
2. Big Volume Group.
3. Scalable Volume Group.

Normal Volume Group
Normal Volume Group can have up to 32 Physical Volumes and 255 Logical Volumes.

Big Volume Group
Big Volume Group can have 128 Physical Volumes and 512 Logical Volumes.

Scalable Volume Group
Scalable Volume Group can have by default 1024 Physical Volumes, 256 Logical Volumes and 32768 Physical Partitions. The number of Logical Volumes can be increased up to 4096and Physical Partitions can also be increased.

Classification on The Basis of Concurrency
I am just listing these. If you want more details please see my previous article Non Concurrent, Concurrent and Enhanced Concurrent Volume Groups. The volume groups can be classified as:

• Non-Concurrent Volume Group.
• Concurrent Volume Group.
• Enhanced Concurrent Volume Group.

Next time I’ll be discussing some other aspects of Volume Groups.