FastResync (FR) FastResync is a part of the Veritas FlashSnap feature. FR supports resynchronization of mirrors by copying only changes to the temporarily split mirror by using FR logging. This reduces the time it takes to rejoin a split mirror to the mirror set and also reduces the server CPU cycles needed to complete the resynchronization. This feature’s added functionality makes the process of splitting a mirror off for tasks such as third mirror backup, data mining, and snapshots much easier to implement. FastResync can also be used on ordinary mirrored volumes to speed up resynchronization.