[DRBD-user] high io when diskless node added to the storage pool

[Alex Kolesnik]

Hi,

I have 3 proxmox nodes and just two of them have drbd storage backend:
LINSTOR ==> sp list
╭─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
┊ StoragePool ┊ Node     ┊ Driver   ┊ PoolName             ┊ FreeCapacity ┊ TotalCapacity ┊ SupportsSnapshots ┊ State ┊
╞═════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╡
┊ drbdpool    ┊ vm-box-2 ┊ LVM_THIN ┊ vg_vm-box-2/drbdpool ┊   297.99 GiB ┊       300 GiB ┊ true              ┊ Ok    ┊
┊ drbdpool    ┊ vm-box-4 ┊ LVM_THIN ┊ vg_vm-box-4/drbdpool ┊   297.99 GiB ┊       300 GiB ┊ true              ┊ Ok    ┊
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

It used to work well moving VMs' virtual drives back and forth from local
storage to drbdpool.

After adding a diskless node to the pool:
LINSTOR ==> sp list
╭─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
┊ StoragePool ┊ Node     ┊ Driver   ┊ PoolName             ┊ FreeCapacity ┊ TotalCapacity ┊ SupportsSnapshots ┊ State ┊
╞═════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╡
┊ drbdpool    ┊ vm-box-2 ┊ LVM_THIN ┊ vg_vm-box-2/drbdpool ┊   297.99 GiB ┊       300 GiB ┊ true              ┊ Ok    ┊
┊ drbdpool    ┊ vm-box-3 ┊ DISKLESS ┊                      ┊              ┊               ┊ false             ┊ Ok    ┊
┊ drbdpool    ┊ vm-box-4 ┊ LVM_THIN ┊ vg_vm-box-4/drbdpool ┊   297.99 GiB ┊       300 GiB ┊ true              ┊ Ok    ┊
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

moving  a drive to drbdpool increases nodes' IO enormously while nothing seems to
be  going on (well, the disk seems to be moving but VERY slow). The log displays
just this w/o any progress, so I had to stop the disk moving:
create full clone of drive scsi0 (LVM-Storage:126/vm-126-disk-0.qcow2)
trying to acquire cfs lock 'storage-drbdpool' ...
transferred: 0 bytes remaining: 10739277824 bytes total: 10739277824 bytes progression: 0.00 %

Did I miss something in the linstor configuration?

PS Am I correct that redundancy should be kept as 2 (in /etc/pve/storage.cfg)
when only two nodes have drbd storage backends?

-- 
Best regards,
Alex Kolesnik