Limitations for logical storage management
The following table shows the limitations for logical storage management.
Although the default maximum number of physical volumes per volume group is 32 (128 for a big volume group, 1024 for a scalable volume group), you can set the maximum for user-defined volume groups when you use the mkvg command. For the rootvg, however, this variable is automatically set to the maximum by the system during the installation.
| Category | Limit |
|---|---|
| Volume group |
Note: The device table on the 64 bit kernel restricts the number
of active major numbers to 1024. Consequently, the number of active
volume groups is restricted to less than 1024 volume groups.
|
| Physical volume | (MAXPVS/volume group factor) per volume group. MAXPVS is 32 for a standard volume group, 128 for a big volume group, and 1024 for a scalable volume group. |
| Physical partition | Normal and Big Volume groups: (1016 x volume group factor) per physical volume up to 1024 MB each in size. Scalable volume groups: 2097152 partitions up to 128 GB in size. There is no volume group factor for scalable volume groups. |
| Logical volume | MAXLVS per volume group, which is 255 for a standard volume group, 511 for a big volume group, and 4095 for a scalable volume group. |
If you previously created a volume group before the 1016 physical partitions per physical volume restriction was enforced, stale partitions (no longer containing the most current data) in the volume group are not correctly tracked unless you convert the volume group to a supported state. You can convert the volume group with the chvg -t command. A suitable factor value is chosen by default to accommodate the largest disk in the volume group.
For example, if you created a volume group with a 9 GB disk and 4 MB partition size, this volume group will have approximately 2250 partitions. Using a conversion factor of 3 (1016 * 3 = 3048) allows all 2250 partitions to be tracked correctly. Converting a standard or big volume group with a higher factor enables inclusion of a larger disk of partitions up to the 1016* factor. You can also specify a higher factor when you create the volume group in order to accommodate a larger disk with a small partition size.
These operations reduce the total number of disks that you can add to a volume group. The new maximum number of disks you can add would be a MAXPVS/factor. For example, for a regular volume group, a factor of 2 decreases the maximum number of disks in the volume group to 16 (32/2). For a big volume group, a factor of 2 decreases the maximum number of disks in the volume group to 64 (128/2).
LVM device size limits
The following limits are the LVM architectural limits. If LVM Bad Block Relocation is required, then PV sizes cannot be larger than 128 GB. For size limitations of specific storage devices, refer to the storage device documentation.
The following size limits are for a 64–bit kernel:
- Original VG
- PV Limit: 1GB (PP) * 16256 (PPs/PV, factor=16) = 15.9 TB
- Big VG
- PV Limit: 1GB (PP) * 65024 (PPs/PV, factor=64) = 63.5 TB
- SVG
- PV & LV Limit: 128GB (PP) * 2048K (PPs/PV) = 256 PB
The following size limits are for a 32–bit kernel:
- All VG Types
- PV Limit: < 1 TB