[DRBD-user] linstor-proxmox : online grow of resources

Julien Escario julien.escario at altinea.fr
Mon Sep 24 13:03:14 CEST 2018

When trying to resize disk (aka grow only) on Proxmox interface for a
linstor-backed device, this error is thrown :
VM 2000 qmp command 'block_resize' failed - Cannot grow device files (500)

BUT resource is effectively growed in linstor and out of sync datas are synced.
drbdpool/vm-2000-disk-1_00000  27,2G  6,91T  27,2G  -

VM is never informed of the resize and Proxmox interface still display old size.

Simply rebooting the VM make it aware of new size, even if Proxmox interface
still display old size.

Offline grown (when VM is stopped) is working perfectly fine, even if resource
was resized online previously (10G creation + 5G online + 5G offline shows 20G
in interface).

At last remark, still for the same resource, ZFS shows much larger volume :
┊ ResourceName   ┊ VolumeNr ┊ VolumeMinor ┊ Size   ┊ State ┊
┊ vm-2000-disk-2 ┊ 0        ┊ 1003        ┊ 26 GiB ┊ ok    ┊

# zfs list drbdpool/vm-2000-disk-2_00000
NAME                            USED  AVAIL  REFER  MOUNTPOINT
drbdpool/vm-2000-disk-2_00000  41,6G  6,87T  41,6G  -

This is just after full resync (resource delete/create on this node).

41GB used for a 26GB volume isn't a bit much ?
Using zpool history, I can find the used line for this resource :
2018-09-24.12:14:43 zfs create -s -V 27268840KB drbdpool/vm-2000-disk-2_00000

= 26GB.

But perhaps is it more realted to ZFS configuration (ashift for example).

Best regards,
Julien Escario

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