To provide point-in-time data protection, when a SyncIQ job starts, it automatically generates a snapshot of the dataset on the source cluster. After it takes a snapshot, it bases all replication activities (scanning, data transfer) on the snapshot view. Subsequent changes to the file system while the job is in progress will not be propagated; those changes will be picked up the next time the job runs. OneFS creates instantaneous snapshots before the job begins – applications remain online with full data access during the replication operation.
Note: This source-cluster snapshot does not require a SnapshotIQ module license. Only the SyncIQ license is required.
Source-cluster snapshots are named SIQ-<policy-id>-[new, latest], where <policy-id> is the unique system-generated policy identifier. SyncIQ compares the newly created snapshot with the one taken during the previous run and determines the changed files and blocks to transfer. Each time a SyncIQ job completes, the associated ‘latest’ snapshot is deleted and the previous ‘new’ snapshot is renamed to ‘latest’.
Note: A SyncIQ snapshot should never be deleted. Deleting a SyncIQ snapshot breaks a SyncIQ relationship, forcing a resync.
Regardless of the existence of other inclusion or exclusion directory paths, only one snapshot is created on the source cluster at the beginning of the job based on the policy root directory path.
Note: Deleting a SyncIQ policy also deletes all snapshots created by that policy.
When a SyncIQ job starts, if a previous source-cluster snapshot is detected, SyncIQ sends to the target only those files that are not present in the previous snapshot, as well as changes to files since the last source-cluster snapshot was taken. Comparing two snapshots to detect these changes is a much more lightweight operation than walking the entire file tree, resulting in significant gains for incremental synchronizations after the initial full replication.
If there is no previous source-cluster snapshot (for example, if a SyncIQ job is running for the first time), a full replication will be necessary.
When a SyncIQ job completes, the system deletes the previous source-cluster snapshot, retaining the most recent snapshot to be used as the basis for comparison on the next job iteration.