VMware ESX Backup fails with “missing size line from sendbackup” and “A file was not found”

Issue Symptoms

FAILURE DUMP SUMMARY:
127.0.0.1 "\esx-hostnamedatastorevm-name" lev 0 FAILED [missing size line from sendbackup]

Issue Description

• You see “missing size line from sendbackup” in the FAILURE DUMP SUMMARY for VMware ESX backups.
• In the FAILED DUMP DETAILS, you see “A file was not found”, as in the example below:

FAILED DUMP DETAILS:
/-- 127.0.0.1 "\\esx-hostname\datastore\vm-name" lev 0 FAILED [missing size line from sendbackup]
[...snip...]
? stdout: Error: [amvmware-disk-helper.cc:154] 4 A file was not found

Resolution

“A file was not found” generally occurs when the guest OS is running Windows and the disk.EnabledUUID VM parameter is set to true. To resolve this, please use the following procedure in a vSphere client:

1. Power down the VM
2. Edit VM Settings > Options > General (under Advanced) > Configuration Parameters
3. Change value of disk.EnableUUID from true to false
4. Save the settings
5. Power on the virtual machine

Changing this value changes the backup from an application-consistent backup to a crash-consistent backup. However, this is the only known way to resolve the issue.