How upgrade a 3 node, 2 node storage, drbd9

[mmenaz]

I've a 3 node cluster (but only 2 node storage) with enterprise repo and drbdmanage 0.91-1, so I think I'd better upgrade now (also hoping 0.97.3-1 will fix some issues about calculated free space) since the license change and waiting to things to clarify (and in the future avoid the no-more-free-as-in-speach drbd9).
How do I have to procede? I would stopp all the vms, backup them, and then? Upgrade first the node without storage, then node2 and last node3 and then reboot all 3 all? Upgrade and reboot each node at rotation?
Is the fist time I do this and dont' know if something can break if I don't do it right.
Current version running is:

root@prox01:~# pveversion -v
proxmox-ve: 4.1-39 (running kernel: 4.2.8-1-pve)
pve-manager: 4.1-22 (running version: 4.1-22/aca130cf)
pve-kernel-4.2.6-1-pve: 4.2.6-36
pve-kernel-4.2.8-1-pve: 4.2.8-39
lvm2: 2.02.116-pve2
corosync-pve: 2.3.5-2
libqb0: 1.0-1
pve-cluster: 4.0-36
qemu-server: 4.0-64
pve-firmware: 1.1-7
libpve-common-perl: 4.0-54
libpve-access-control: 4.0-13
libpve-storage-perl: 4.0-45
pve-libspice-server1: 0.12.5-2
vncterm: 1.2-1
pve-qemu-kvm: 2.5-9
pve-container: 1.0-52
pve-firewall: 2.0-22
pve-ha-manager: 1.0-25
ksm-control-daemon: 1.2-1
glusterfs-client: 3.5.2-2+deb8u1
lxc-pve: 1.1.5-7
lxcfs: 2.0.0-pve2
cgmanager: 0.39-pve1
criu: 1.6.0-1
zfsutils: 0.6.5-pve7~jessie
drbdmanage: 0.91-1

 

[mmenaz]

Ok, I've upgraded first the "control node", then rebooted. Then I upgraded the node with storage but no VM on it, and rebooted. Last I upgraded the node with storage where VM are run (primary), and rebooted. Everything went fine, fortunately.
The only big problem is that still, with 2x800GB for drbd9 in each of the 2 nodes, and 800GB of total disk sizes, the Proxmox gui shows 2.6TB used over 2.8T total! How to fix it if possible? I thought that latest drbd9 release had this bug solved