Make application-consistent virtual machine backups
Ask the guest to flush databases before the hypervisor copies disks, or the restored machine may boot with a torn write.
A crash-consistent copy is whatever was on disk at the instant of the snapshot. Most file systems repair that on boot. A database may replay logs, or it may refuse to open if a transaction was half written.
Application-consistent jobs call VSS on Windows or a pre-freeze script on Linux so the database writes its logs and pauses writes. After the snapshot, the post-thaw script lets traffic resume. Test that the scripts exist on the guest and that the backup report says the quiesce succeeded.
If the guest cannot be quiesced, take a dump from the database itself and store that dump with the virtual machine backup.