PowerFlex: SCSI Unmap/Datastore Reclaim Does Not Work On PowerFlex OS Thin Volumes

Scenario

Due to a requirement by vSphere ESXi of the partition table to begin above sector 2048 (1 MB), the thin volumes that were upgraded from older versions do not reclaim space during SCSI unmap processes. 

Symptoms

Errors in the vmkernel logs:

2018-03-16T08:54:48.006Z cpu30:67545 opID=56d7b237)FSDisk: 286: 

Issue of delete blocks failed [sync:1] numDescs one Address is not aligned on required boundary 0x439d40f1e5c0. We can see that the partitions are starting from sector "128," which is only 64 K:

$ grep -A 5 'Device: .*eui' esx-vdi-domain.com-2018-03-07--19.09/commands/partedUtil.sh.txt
Device:  /vmfs/devices/disks/eui.1ace4f754e66fd1c95f1d8aa00000003
Partition table:
unknown
0 255 63 1

Usable sectors:
--
Device:  /vmfs/devices/disks/eui.1ace4f754e66fd1ccb81e13f00000000
Partition table:
gpt
534698 255 63 8589934592
1 128 8589934552 AA31E02A400F11DB9590000C2911D1B8 vmfs 0

--
Device:  /vmfs/devices/disks/eui.1ace4f754e66fd1ccb81e14000000001
Partition table:
gpt
534698 255 63 8589934592
1 128 8589934552 AA31E02A400F11DB9590000C2911D1B8 vmfs 0

Impact

Space on the thin VxFlex Datastores is unable to be reclaimed.

In order for a VxFlex thin provisioned volume to be reclaimable, the Datastore partition must start above sector 1024 when created.

From the vmsupport, we can see that each of the VxFlesOS volumes has only one partition on them, which starts at sector 128 (64 K). According to VMware's own KB Thin Provisioning Block Space Reclamation (VAAI UNMAP) does not work  VAAI unmap only works.

On SAN arrays where the partition offset is a multiple of 1 MB.

Also from VMware KB (Using partedUtil command-line disk partitioning utility on ESXi 

Note: Volumes that are upgraded from VMFS-3 to VMFS-5 continue to have the VMFS partition starting at sector 128, rather than at sector 2048.

Workaround

Create new Volumes and Datastores within the environment. Validate the partitions begin at or above 2048 (1 MB) and then perform Storage vMotions from the old Datastores to the new. 

Impacted Versions

All

Fixed In Version

N/A