Calculating the overhead required by snapshot files

When creating a snapshot for the virtual machine, you experience these symptoms:

• In the vSphere Client, you see the error:

  File is larger than the maximum size supported by datastore
   

• In the /var/log/vmware/hostd.log file, you see the error:

  Snapshot guest failed: The file is too big for the filesystem.

  Calculating the overhead required by snapshot files

  The failure depends on the size of the virtual disk. All virtual machines having disks with a maximum supported size by VMFS may experience this error.
   
  For example, a virtual machine with a disk sized 256 GB stored on VMFS with 1MB block size fails to snapshot because of the additional overhead required for the delta files. Though the maximum file size for a 1MB block size is 256GB – 512, creating a vmfsSparse (delta) disk requires additional overhead space about 2GB. This resulting delta has potential to grow beyond the file system limit.
  To resolve this issue, move the virtual machine to a VMFS volume with a larger block size.
   
  Overhead for the snapshot is roughly about 2GB for a disk size of 256GB. If snapshots are to be used, consider the overhead while deciding the size of the disks.
   
  Note: VMware recommends that you to create virtual disks of size less than 2TB-xxGB, to use features like Snapshot, Clone, and Independent-nonpersistent.
   

  Block size in MB	Maximum VMDK size	Maximum Overhead
  1	256 GB – 512 B	~ 2 GB
  2	512 GB – 512 B	~ 4 GB
  4	1024 GB – 512 B	~ 8 GB
  8	2048 GB – 512 B	~ 16 GB

   
  This means that to use snapshots, the maximum file sizes are:
   
  1MB block size -> 256GB – 2GB = 254GB
  2MB block size -> 512GB – 4GB = 508GB
  4MB block size -> 1024GB – 8GB = 1016GB
  8MB block size -> 2048GB -16GB = 2032GB