Datastore Grow
Below are steps to grow an existing datastore in a Proxmox cluster.
It is assumed that the volume has already been grown on the relevant storage device. If not, look at Volume/LUN Tasks to grow the volume
Log into VAP node that you extended the volume on
iSCSI Rescan
Inform the hosts to check the device paths
Multipath Rescan
Inform the multipath drivers to update, based on the previous rescan
Add volume to LVM
Run a scan to detect the increased volume size
Physical Volume
Get the mpath name of the volume you are working on with something like multipath -l as you will need to grow the physical volume information based on this (e.g. mpathd is the new device, so our dev mapper would be /dev/mapper/mpathd)