Error creating virtual machine snapshot, "An error occurred while saving the snapshot: msg.changetracker.CREATEMIRROR."

Products

• VMware vCenter Server

Issue/Introduction

• Attempting to create a snapshot of the Virtual Machine, reports the following error on the vCenter UI :

"An error occurred while saving the snapshot: msg.changetracker.CREATEMIRROR." 

• The following related log entries are observed for the virtual machine :

       /var/log/vpxa.log

      2026-02-24T09:42:28.529Z Er(163) Vpxa[2101309]: -->          message = "An error occurred while saving the snapshot: Could not create mirror of change tracking file."
      2026-02-24T09:42:28.529Z Er(163) Vpxa[2101309]: -->       },
      2026-02-24T09:42:28.529Z Er(163) Vpxa[2101309]: -->       (vmodl.LocalizableMessage) {
      2026-02-24T09:42:28.529Z Er(163) Vpxa[2101309]: -->          key = "msg.snapshot.vigor.take.error",
      2026-02-24T09:42:28.529Z Er(163) Vpxa[2101309]: -->          arg = (vmodl.KeyAnyValue) [
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->             (vmodl.KeyAnyValue) {
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->                key = "1",
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->                value = "msg.changetracker.CREATEMIRROR"
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->             }
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->          ],
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->          message = "An error occurred while taking a snapshot: Could not create mirror of change tracking file."
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->       }
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->    ],
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->    reason = "An error occurred while saving the snapshot: Could not create mirror of change tracking file."
      2026-02-24T09:42:28.530Z Er(163) Vpxa[2101309]: -->    msg = "An error occurred while saving the snapshot: Could not create mirror of change tracking file."


      vmware.log

     2026-02-24T09:42:28:37.059Z Er(02) vmx 7a31ad25-b0-c62d DISKLIB-LIB_CREATE   : DiskLib_NotifySnapshotPrepare: FiltLib failed to notify snapshot prepare: Operation completes asynchronously
    2026-02-24T09:42:28:37.092Z Wa(03) vmx 7a31ad25-b0-c62d DISKLIB-CBT   :ChangeTrackerESX_CreateMirror: Failed to grow destination file /vmfs/volumes/vsan:52b1eca9baeb039c-69870ffb0aaa28b5/xxxxxx-a2af-77d4-de7b-xxxxxxxx/xxxxxxx-    ctk-mirror.vmdk to 9175552 bytes.
    2026-02-24T09:42:28.092Z Wa(03) vmx 7a31ad25-b0-c62d DISKLIB-CTK   :ChangeTracker_Mirror: Failed to create mirror node.
     2026-02-24T09:42:28.101Z Wa(03) vmx 7a31ad25-b0-c62d DISKLIB-LIB_BLOCKTRACK   : DiskLibBlockTrackPrepareChild: Failed to mirror tracking info file /vmfs/volumes/vsan:52b1eca9baeb039c-xxxxxxxxx/71c6ee67-a2af-77d4-de7b-xxxxxxx/xxxxxx2-ctk.vmdk: Could not create mirror of change tracking file (5948).

 

   /var/run./log/vmkernel.log


   2026-02-24T09:42:28.687Z In(182) vmkernel: cpu56:2097725)Fil6: 4308: '71c6ee67-a2af-77d4-de7b-xxxxxxx': Fil6 file IO (<FD c14 r104>) : No space left on device
   2026-02-24T09:42:28.687Z In(182) vmkernel: cpu56:2097725)Fil6: 4270: ioCtx: 0x45de51dfe900, world: 2097725, overallStatus: No space left on device, token: 0x0, tokenStatus: N, txnToken: 0x0, txnTokenStatus: N, totalIOSize: 260760, maxIOLength: 260760
   2026-02-24T09:42:28.687Z In(182) vmkernel: cpu56:2097725)Fil6: 4278: numAddrs: 0, numTbz: 0, numPBsToAlloc: 0, numBlocksToAlloc: 1 numTBZBlocks: 0, numPBsToUnmap: 0, numBlocksToUnmap: 0
   2026-02-24T09:42:28.687Z In(182) vmkernel: cpu56:2097725)Fil6: 4284: opType: 2, ioFlags: 131408, allocFlags: 0, ioStateTxn: 0, ioStateNoTxn: 0, txnState: 3, numResolvedAddrMaps: 0, numTxnPendingAddrMaps: 64
   2026-02-24T09:42:28.687Z In(182) vmkernel: cpu56:2097725)Fil6: 4291: wakeupOnIOComplete: 0, isIOIssued: 0, isIODone: 0, isRead: 0 isSync: 1, canBlock: 1, lastPartialBlock: 0
   2026-02-24T09:42:28.705Z In(182) vmkernel: cpu56:2097725)Fil3: 11134: SFB totalNumResources: 261120 numFreeResources: 0 numNotAvailable 0
   2026-02-24T09:42:28.706Z In(182) vmkernel: cpu56:2097725)Fil3: 11141: LFB totalNumResources: 510 numFreeResources: 0 numNotAvailable 510
   2026-02-24T09:42:28.706Z In(182) vmkernel: cpu56:2097725)ResAff: 13784: 71c6ee67-a2af-77d4-de7b-xxxxxxx: <FD c14 r104> - NSPC: lt 0 oo 10 nc 1020 nvr 0 ac 0 dl 0 sp 0 pa 0 ma 0 tt 0 rjP 0 rjN 510:No space left     on device

 

Environment

VMware vSAN 8.x

Cause

The snapshot operation fails because CBT mirror file creation cannot proceed due to lack of free space in the VM namespace .Large files placed directly inside the VM namespace can exhaust the available space and prevent metadata operations such as snapshot creation and CBT file generation, vmotion etc. 

vSAN debug object list shows the used space as 255 GB which is the max.

Used:
  364258525184
Used 4K Blocks:
  363375947776 --> 255 GB 
Size:
  273804165120
Type:
  vmnamespace
Path:
  /vmfs/volumes/vsan:52b1eca9baeb039c-XXXXXXXXX/XXXXXXXX(Exists)
Group UUID:
  71c6ee67-a2af-77d4-de7b-XXXXXXX
Directory Name:
  XXXXXXXXX

Resolution

1. Identify the unnecessary files in the VM namespace.
2. Either move the files or delete them if the they are not required.
3. Once the space gets free, perform the snapshot creation should succeed and ctk creation as well.