Case1 ) When a new disk is added ( ex: /dev/sda ), After scanning we create 1 partition for the whole disk ( ex: /dev/sda1 ) and then pvcreate and then add to a volume group.
Query )
We can do directly pvcreate on the whole disk also
So, what is the difference between
pvcreate after creating a single partition on whole disk
Note, however, that the HOWTO is years old. I don't know whether there is newer advice. The advice above still seems to make sense to me.
In my situation, I place a single partition on a disk, then incorporate that into a RAID1 (or RAID10 if I have enough disks), then I place LVM on top of that.
Perhaps someone will stop by with additional information.
4.2.1.1. Setting the Partition Type
If you are using a whole disk device for your physical volume, the disk must have no partition table.
For DOS disk partitions, the partition id should be set to 0x8e using the fdisk or cfdisk command or
an equivalent. For whole disk devices only the partition table must be erased, which will effectively
destroy all data on that disk. You can remove an existing partition table by zeroing the first sector
with the following command:
# dd if=/dev/zero of=PhysicalVolume bs=512 count=1
4.2.1.2. Initializing Physical Volumes
Use the pvcreate command to initialize a block device to be used as a physical volume. Initialization
is analogous to formatting a file system.
Still not much information to draw a conclusion....
By adding whole disk /dev/sda using pvcreate, You can't create other physical volumes on the /dev/sda.
If you create partitions and create physical volumes using pvcreate, You can add other physical volumes of /dev/sda to increase its space.This is called Efficient Disk Space management.
This means you need to depend on other disks like /dev/sdb or /dev/sdc or etc..