2.2. Multiple partitions on a disk
You can create physical volumes (PV) out of disk partitions by using LVM.
Red Hat recommends that you create a single partition that covers the whole disk to label as an LVM physical volume for the following reasons:
- Administrative convenience
- It is easier to keep track of the hardware in a system if each real disk only appears once. This becomes particularly true if a disk fails.
- Striping performance
- LVM cannot tell that two physical volumes are on the same physical disk. If you create a striped logical volume when two physical volumes are on the same physical disk, the stripes could be on different partitions on the same disk. This would result in a decrease in performance rather than an increase.
- RAID redundancy
- LVM cannot determine that the two physical volumes are on the same device. If you create a RAID logical volume when two physical volumes are on the same device, performance and fault tolerance could be lost.
Although it is not recommended, there may be specific circumstances when you will need to divide a disk into separate LVM physical volumes. For example, on a system with few disks it may be necessary to move data around partitions when you are migrating an existing system to LVM volumes. Additionally, if you have a very large disk and want to have more than one volume group for administrative purposes then it is necessary to partition the disk. If you do have a disk with more than one partition and both of those partitions are in the same volume group, take care to specify which partitions are to be included in a logical volume when creating volumes.
Note that although LVM supports using a non-partitioned disk as physical volume, it is recommended to create a single, whole-disk partition because creating a PV without a partition can be problematic in a mixed operating system environment. Other operating systems may interpret the device as free, and overwrite the PV label at the beginning of the drive.
