[ovirt-users] OVirt 4.1.2 - trim/discard on HDD/XFS/NFS contraproductive

[Markus Stockhausen]

Hi,

we just set up a new 4.1.2 OVirt cluster. It is a quite normal
HDD/XFS/NFS stack that worked quit well with 4.0 in the past.
Inside the VMs we use XFS too.

To our surprise we observe abysmal high IO during mkfs.xfs
and fstrim inside the VM. A simple example:

Step 1: Create 100G Thin disk
Result 1: Disk occupies ~10M on storage

Step 2: Format disk inside VM with mkfs.xfs
Result 2: Disk occupies 100G on storage

Changing the discard flag on the disk does not have any effect.

Am I missing something?

Best regards.

Markus
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