Space Reclamation commands with certain Linux guest operating systems fail to work after Storage vMotion of the virtual machine

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:
Certain Linux guest operating systems stop sending unmap commands after live disk migration (Storage vMotion) or live disk consolidation.

Environment

VMware vSphere ESXi 6.5

Cause

During live disk migration or live disk consolidation, guest-initiated unmap requests are not supported by design. Upon completion of such live disk operations, unmap commands should resume normally, if supported by the datastore's filesystem. However, if unmap commands failed while such a live disk operation was in progress, due to being unsupported, then certain guest operating systems may fail to detect changes in unmap support without a reboot, even after the operation completes.

Resolution

RHEL 7.0, with kernel 3.10.0-123, released 2014-06-09 is known to be affected by this issue.
RHEL 7.4, with kernel 3.10.0-693, released 2017-07-31 is known to be unaffected.

Workaround:
To workaround this issue, manually run this command after Storage vMotion or live disk consolidation on the disk with host x, bus y, target z, LUN n:

echo -n unmap > /sys/class/scsi_disk/x:y:z:n/provisioning_mode

This will force unmap operations to resume on the specified disk.

Additional Information

Space Reclamation Requests from Guest Operating Systems