When you create a volume group, four values must be selected:
- size of physical extents for this volume group (PE size: default 4 MB, can be 4, 8, 16, 32, 64, 128 or 256 MB)
- the maximum number of physical extents per physical volume (MaxPE: default is 1016 or appropriate for the physical volume used to create the VG, whichever is larger; maximum is 65535)
- the maximum number of physical volumes for this volume group (MaxPV: default is 16, maximum is 255)
- the maximum number of logical volumes for this volume group (default is 255, which is also the maximum)
These values cannot be changed once the volume group has been created. They will limit the size and number of physical volumes you can use in that volume group. The maximum size of a logical volume is also limited to 65535 extents, as you discovered.
You are requesting a logical volume of 511920 MB in size. The error message reveals it would need 127980 extents to create that, so your PE size is 511920 MB / 127980 = 4 MB, the default value.
The only way you will be able to create a logical volume of that size in that volume group is to destroy the volume group and recreate it with different parameters. You need to back up all the data and restore it to the logical volumes of the re-created volume group.
This is what happens when the creator of the volume group does not plan ahead for expansion in the future (or the need of expansion is severely underestimated).
For modern disks, the PE size of 4 MB is *way* too small. I'd recommend that all VGs for new systems be always created with the PE size of 16 MB or above. For large data VGs, I'd recommend an extent size of at least 64 or 128 MB always if possible. This will also determine the maximum LV size, because it is always 65535 * PE size.
When creating a new volume group, you must also think about the MaxPE value. If you use the default values and the physical volume size divided by the extent size is more than 1016, the current physical volume size gets effectively hardcoded as the maximum physical volume size for that volume group. Since disks are getting bigger all the time, it is very likely the disks you will want to add to the VG in the future are going to be bigger than the current disks.
MK
