Backup is under 1 MB in size

Problem

After backing up a VM with two disks, the backup of the second disk is under 1 MB in size.

Solution

If there is no problem restoring from backup, this is correct behavior.

A backup can be under 1MB in size for two reasons:

• the disk is empty and has not been filled yet. Then the image itself will take up less space. Its size grows as new data appears;
• the disk is filled with repetitive data, therefore it is highly compressible.