Restoring a thin-provisioned disk created on an NFS volume using Virtual Disk Development Kit changes the disk type from thin to thick-provisioned and eager-zeroed
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Restoring a thin-provisioned disk created on an NFS volume using Virtual Disk Development Kit changes the disk type from thin to thick-provisioned and eager-zeroed

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Article ID: 344468

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction



Symptoms:
When restoring a thin-provisioned disk on an NFS volume using Virtual Disk Development Kit, you experience these symptoms:
  • The disk is restored as a thick, eager-zeroed volume.

  • In the /var/log/vpxa.log file, you see entries similar to:
2015-08-24T12:45:32.853Z [3E0EAB70 trivia 'VpxaHalCnxHostagent' opID=WFU-1c6d92bf] [LogObjectUpdate] 154::config.hardware.device[2001].backing.parent changed to:
--> (vim.vm.device.VirtualDisk.FlatVer2BackingInfo) {
--> dynamicType = <unset>,
--> fileName = "[datastore3] t9rest/t9rest.vmdk",
--> datastore = 'vim.Datastore:53887b29-a274c74c-258c-5cf3fc280fe9',
--> backingObjectId = "154-2001-1",
--> diskMode = "persistent",
--> split = <unset>,
--> writeThrough = <unset>,
--> thinProvisioned = false,
--> eagerlyScrub = true,
--> uuid = "6000C298-089e-c8e2-54d5-87a65af1276c",
--> contentId = "f2bfbbe3a24203a8a168d2e3e5618324",
--> changeId = <unset>,
--> parent = (vim.vm.device.VirtualDisk.FlatVer2BackingInfo) null,
--> deltaDiskFormat = <unset>,
--> digestEnabled = <unset>,
--> deltaGrainSize = <unset>,

Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

Environment

VMware Virtual Disk Development 1.2
VMware vSphere ESXi 6.0
VMware vSphere ESXi 5.5
Virtual Disk Development Kit 6.0
Virtual Disk Development Kit 5.5

Cause

NFS hosted virtual disk created as thin-provisioned is first fully written and then marked as thick-provisioned eager-zeroed:
  1. Virtual machine is created thin-provisioned on an NFS datastore.
  2. During its first backup, the virtual machine is fully read and marked fully-written because CBT information is not available for NFS volumes.
  3. On a restore, since the virtual machine virtual disk is read as fully-written, ESXi disk type decision logic marks it as thick and eager-zeroed.

Resolution

This is a known issue affecting VMware ESXi 5.5. Currently, there is no resolution.

To work around the issue, migrate thin-provisioned virtual machines from an NFS datastore to a VMFS datastore for thin-provisioned virtual disk backup or restore operations.


Additional Information

For more information about the cause of this issue, see VDDK restores thin-provisioned disk of a virtual machine residing on NFS as thick-provisioned disk (2077787).

For more information on limitations of CBT in the context of NFS volumes and other causes of thin-provisioned disks restored as thick-provisioned, see vSphere Data Protection restores a thin-provisioned disk as a thick-provisioned disk (2048016)



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vSphere Data Protection restores a thin-provisioned disk as a thick-provisioned disk
VDDK restores thin-provisioned disk of a virtual machine residing on NFS as thick-provisioned disk
NFS ボリュームで作成されたシン プロビジョニング ディスクのバックアップをリストアすると、ディスク タイプがシンからシック プロビジョニング、eager-zeroed に変わる