Snapshot support in Ozone
Learn about different scenarios where you can use snapshots, the snapshot APIs that are available for use, and the snapshot architecture.
- Backup and restore
Create hourly, daily, weekly, or monthly snapshots for backup and recovery..
- Archival and compliance
Take snapshots for compliance purpose and archive them..
- Replication and disaster recovery (DR)
Snapshots provide frozen immutable images of the bucket on the source Ozone cluster. Snapshots can be used for replicating these immutable bucket images to remote DR sites.
- Incremental replication
DistCp with SnapshotDiff offers an efficient way to incrementally sync up source and destination buckets.
ozone shCLI. This feature can also be programmatically accessed from Ozone
ObjectStoreJava client. The feature provides following functionalities:
- Createan instantenous snapshot for a given bucket.
ozone sh snapshot create [-hV] <bucket> [<snapshotName>]
- List all snapshots of a given bucket.
ozone sh snapshot list [-hV] <bucket>
- Delete a specific snapshot for a given bucket.
ozone sh snapshot delete [-hV] <bucket> <snapshotName>
- Given two snapshots, list all the keys that are different between them.-
ozone sh snapshot diff [-chV] [-p=<pageSize>] [-t=<continuation-token>] <bucket> <fromSnapshot> <toSnapshot>
SnapshotDiff functionality in CLI/API is asynchronous. The first time the
API is invoked, Ozone Manager (OM) starts a background thread to calculate the
SnapshotDiff, and returns
Retry with suggested duration
for the retry operation. After the SnapshotDiff is computed, this API returns the
differences in multiple pages. Within each
SnapshotDiff response, OM also
returns a continuation token for the client to continue from the last batch of
SnapshotDiff results. This API is safe to be called multiple times for a
given snapshot source and destination pair. Internally, each OM computes
SnapshotDiff only once and stores it for future invocations of the same
Ozone snapshot architecture leverages the fact that data blocks once written, remain immutable
for their lifetime. These data blocks are reclaimed only when the object key metadata that
references them, is deleted from the Ozone namespace. All of this Ozone metadata are stored
on the OM nodes in the Ozone cluster. When you take a snapshot of an Ozone bucket,
internally the system takes snapshot of the Ozone metadata in OM nodes. Since Ozone does not
allow updates to DataNode blocks, integrity of data blocks referenced by Ozone metadata
snapshot in OM nodes remains intact. Ozone key deletion service is also aware of Ozone
snapshots. Key deletion service does not reclaim any key as long as it is referenced by the
active object store bucket or any of its snapshot. When the snapshots are deleted, a
background garbage collection service reclaims any key that is not part of any snapshot or
active object store. Ozone also provides the SnapshotDiff API. Whenever a
user issues a
SnapshotDiff between two snapshots, it efficiently calculates
all the keys that are different between these two snapshots and returns paginated
SnapshotDiff list result.