I have a CloudServer with 3 disks

/dev/sda -> /       30G
/dev/sdb -> /vm    100G --> /dev/vmvg
/dev/sdc -> /media  20G --> /dev/media/lv

As customer VMs, on sdb have grown, I need to add more disk.
Luckily for me this cloudserver has SAN storage, so I can increase by /dev/sdb disk 150G on the fly.

That’s great, but when I do a vgdisplay -v vmvg, it still shows 100G

Now there are all kinds of ways documented on the internet, but here is the real answer.

If you are using SAN disks, DO NOT use /dev/sdb1, /dev/sdb2 etc just use /dev/sdb

If you did that then the increase is size is not seen immediately and a reboot would not actually help.

So if you have added the whole disk to a volume group rather than a partition, you can use the following command to bring the extra extents available into the volume group.

pvresize /dev/sdb

Now a vgdisplay -v vmvg will show the extra extents, leaving an lvextend and a resize2fs to make the space available in the filesystem.