Proxmox - boiled down iSCSI multipath configuration

This post is based on Proxmox's official multipath guide https://pve.proxmox.com/wiki/Multipath, after trial an error we believe we have been able to distil it down to a few core steps, hope this is as useful to you as it is to us.

Some steps are to be done in all of your hosts while some others can be done within a single host, we have tried our best to deferentiate them at each step.

We assume the following;

1. You have 2 network paths dedicated to iSCSI, 110 and 111.
2. These network interfaces for iSCSI have been named iscsi-110 and iscsi-111, we can add details about this if required, send us a message.
3. Test LUN name generic-vm01.
4. You are using TrueNAS.

Add new iSCSI LUN

In all nodes

# add iSCSI target via both paths
iscsiadm -m node --targetname iqn.2005-10.org.freenas.ctl:generic-vm01 --portal 10.22.110.104:3260 -I iscsi-110 --op=new
iscsiadm -m node --targetname iqn.2005-10.org.freenas.ctl:generic-vm01 --portal 10.22.111.104:3260 -I iscsi-111 --op=new
# login to the target
iscsiadm -m node -T iqn.2005-10.org.freenas.ctl:generic-vm01 -l
# verify session is active
iscsiadm -m session

In a single node

# find new block devices
lsblk
# you should see the devices at the very bottom, match size or other details
# get the WWID of the new disk (replace sde with your new disk), this assumes we are dealing with device called sde
/lib/udev/scsi_id -g -u -d /dev/sde

In all nodes

# register WWID  
multipath -a <WWID>
# refresh 
multipath -r
# verify multipath device is present
multipath -ll

In a single node

# create the physical volume
pvcreate /dev/mapper/<WWID>
# create the volume group (this is where you define the name)
vgcreate generic-vm01 /dev/mapper/<WWID>

In all nodes

# refresh LVM cache so other nodes see the new VG
pvscan --cache

Proxmox UI

Datacenter → Storage → Add → LVM → Existing volume groups → generic-vm01 → Shared