31362: Acronis Products: Virtual machine backup fails with "Awaiting task 'CreateSnapshot' has failed. Reason: File is larger than the maximum size supported by datastore"

Last update: Thu, 2016-03-31 14:56

You attempt to run a backup from virtual guest and get this error. Change location of virtual guest or change block size of used datastore, so that the datastore blocksize and blocksize of virtual guest matches.


Backup of specific virtual machine using the Virtual Appliance fails with

Awaiting task 'CreateSnapshot' has failed. Reason: File <unspecified filename> is larger than the maximum size supported by datastore '<unspecified datastore>


This error occurs if VMX file is located in a datastore whose block size does not support the size of the VMDK file for that virtual machine.

(!) VMware creates snapshot in the directory where VMX file is located. 

Table below has the details about the block size and supported VMDK size.

Block size in MB

Maximum VMDK size

Maximum Overhead


256 GB - 512 B

~ 2 GB


512 GB - 512 B

~ 4 GB


1024 GB - 512 B

~ 8 GB


2048 GB - 512 B

~ 16 GB



  1. Move the VMX file to a different data store whose block size supports the size of VMDK for that virtual machine. Refer to the VMware Knowledge Base link for further details: Moving or copying a virtual machine within a VMware environment
  2. Please edit the VMX file, so that snapshots will be created on a different datastore that has a bigger block size. Refer to the VMware Knowledge Base link for further details: Creating snapshots in a different location than default virtual machine directory


In ESX 5.0 and 5.1 VMFS 5 file system is present which has fixed 1 MB block size. The maximum virtual disk (VMDK) size limit for snapshot operations is 2 TB minus 512 B.

Therefore, snapshot operations are not possible for VMDK file with size larger than 2 TB minus 512 B. We need to keep the VMDK size less than or equal to maximum supported size.

You may also read more about this limitation here: