PHD Virtual Backup makes use of hard links when deduplicating Virtual Full backup data on the backup data store.
A hard link is essentially a reference to a file or directory on a file system. PHD Virtual Backup makes use of hard links when deduplicating Virtual Full backup data on the backup data store. Because of this, hard links must be supported and enabled (if necessary) on any storage device used as a backup target for Virtual Full backups. By default, most storage device file systems support hard links and have them enabled - if your storage device supports hard links but does not have them enabled, refer to your vendor's documentation for details on enabling them.
Note: Storage devices used for Full/Incremental backups do not require hard link support.
If hard links are not supported or enabled for your backup storage location, a warning message is logged after defining the backup storage and restarting the PHD VBA. If you attempt to run a Virtual Full backup with storage configured that does not support hard links, you will encounter the following error, BDS incompatible with virtual-full job: Hard links are not supported.
Please NOTE: If prior backups to this same storage were successful, you may have encountered a defect that is corrected with version PHDVB 6.5.2 and later