SUMMARY
Job schedule can be configured to run as frequently as every 15 minutes.
ISSUE
PHDVB 6.5 was enhanced to allow for granular backups and replication within a single job,as frequently as every 15 minutes.
Another option is to create any number of customized jobs to protect your virtual machines. For example, you could create a job that backs up all of your VMs each night, then create another job that runs in the afternoon for specific VMs that have shorter RPO requirements.