Table of Contents
MinIO supports server-side and client-side replication of objects between source and destination buckets.
- Server-Side Bucket Replication
Configure per-bucket rules for automatically synchronizing objects between MinIO deployments. The deployment where you configure the bucket replication rule acts as the “source” while the configured remote deployment acts as the “target”. MinIO applies rules as part of object write operations (e.g.
PUT) and automatically synchronizes new objects and object mutations, such as new object versions or changes to object metadata.
MinIO server-side bucket replication only supports a MinIO cluster on an identical release for the remote replication target.
- Client-side Bucket Replication
Use the command process to synchronize objects between buckets within the same S3-compatible cluster or between two independent S3-compatible clusters. Client-side replication using
mc mirrorsupports MinIO-to-S3 and similar replication configurations.
Bucket vs Site Replication
Bucket Replication is distinct from and mutually exclusive with site replication.
Bucket Replication synchronizes data at the bucket level, such as bucket prefix paths and objects.
You can configure bucket replication at any time, and the remote MinIO deployments may have pre-existing data on the replication target buckets.
Site Replication extends bucket replication to include IAM, security tokens, access keys, and bucket-level configurations.
Site replication is typically configured when initially deploying the MinIO peer sites. Only one site can hold any bucket or objects at the time of initial configuration.
Server-Side Bucket Replication
MinIO server-side bucket replication is an automatic bucket-level configuration that synchronizes objects between a source and destination bucket. MinIO server-side replication requires the source and destination bucket be two separate MinIO clusters running the same MinIO Server version.
For each write operation to the bucket, MinIO checks all configured replication rules for the bucket and applies the matching rule with highest configured priority. MinIO synchronizes new objects and object mutations, such as new object versions or changes to object metadata. This includes metadata operations such as enabling or modifying object locking or retention settings.
MinIO server-side bucket replication is functionally similar to Amazon S3 replication while adding the following MinIO-only features:
Source and destination bucket names can match, supporting site-to-site use cases such as Splunk or Veeam BC/DR.
Simplified implementation than S3 bucket replication configuration, removing the need to configure settings like AccessControlTranslation, Metrics, and SourceSelectionCriteria.
Active-Active (Two-Way) replication of objects between source and destination buckets.
Multi-Site replication of objects between three or more MinIO deployments
Resynchronization (Disaster Recovery)
Resynchronization primarily supports recovery after partial or total loss of the
data on a MinIO deployment using a healthy deployment in the replica
configuration. Use the
mc replicate resync command completely
resynchronize the remote target (
mc admin bucket remote) using the
specified source bucket.
The resynchronization process checks all objects in the source bucket against all configured replication rules that include existing object replication. For each object which matches a rule, the resynchronization process places the object into the replication queue regardless of the object’s current replication status.
MinIO skips synchronizing those objects whose remote copy exactly match the source, including object metadata. MinIO otherwise does not prioritize or modify the queue with regards to the existing contents of the target.
mc replicate resync operates at the bucket level and does
not support prefix-level granularity. Initiating resynchronization on a large
bucket may result in a significant increase in replication-related load
and traffic. Use this command with caution and only when necessary.
For buckets with object transition (Tiering) configured, replication resynchronization restores objects in a non-transitioned state with no associated transition metadata. Any data previously transitioned to the remote storage is therefore permanently disconnected from the remote MinIO deployment. For tiering configurations which specify an explicit human-readable prefix as part of the remote configuration, you can safely purge the transitioned data in that prefix to avoid costs associated to the “lost” data.
Replication of Delete Operations
MinIO supports replicating delete operations, where MinIO synchronizes deleting specific object versions and new delete markers. Delete operation replication uses the same replication process as all other replication operations.
MinIO requires explicitly enabling versioned deletes and delete marker
replication . Use the
mc replicate add --replicate field to
specify both or either
delete-marker to enable versioned
deletes and delete marker replication respectively. To enable both, specify both
strings using a comma separator
For delete marker replication, MinIO begins the replication process after
a delete operation creates the delete marker. MinIO uses the
X-Minio-Replication-DeleteMarker-Status metadata field for tracking
delete marker replication status. In
replication configurations, MinIO may produce duplicate delete markers if
both clusters concurrently create a delete marker for an object or
if one or both clusters were down before the replication event synchronized.
For replicating the deletion of a specific object version, MinIO marks the
object version as
PENDING until replication completes. Once the remote
target deletes that object version, MinIO deletes the object on the source.
While this process ensures near-synchronized version deletion, it may result
in listing operations returning the object version after the initial
delete operation. MinIO uses the
tracking delete version replication status.
MinIO only replicates explicit client-driven delete operations. MinIO does not replicate objects deleted from the application of lifecycle management expiration rules. For active-active configurations, set the same expiration rules on all of of the replication buckets to ensure consistent application of object expiration.
MinIO Trims Empty Object Prefixes on Source and Remote Bucket
If a delete operation removes the last object in a bucket prefix, MinIO
recursively removes each empty part of the prefix up to the bucket root.
MinIO only applies the recursive removal to prefixes created implicitly as
part of object write operations - that is, the prefix was not created using
an explicit directory creation command such as
If a replication rule enables replication delete operations, the replication process also applies the implicit prefix trimming behavior on the destination MinIO cluster.
For example, consider a bucket
photos with the following object prefixes:
photos/NYE21 is the only prefix explicitly created using
All other prefixes were implicitly created as part of writing the object
located at that prefix.
A command removes
myphoto.jpg. MinIO automatically trims the empty
A command then removes the
myotherphoto.jpg. MinIO automatically trims the
/februaryprefix and the now-empty
A command removes the
NewYears.jpgobject. MinIO leaves the
/NYE21prefix remains in place since it was explicitly created.
Replication of Existing Objects
MinIO by default does not enable existing object replication. Objects
created before replication was configured or while replication is
disabled are not synchronized to the target deployment.
mc RELEASE.2021-06-13T17-48-22Z and
RELEASE.2021-06-07T21-40-51Z, MinIO supports enabling
replication of existing objects in a bucket.
Enabling existing object replication marks all objects or object prefixes that satisfy the replication rules as eligible for synchronization to the source cluster, even if those objects were created prior to configuring or enabling replication. You can enable existing object replication while configuring or modifying a replication rule:
For new replication rules, include
"existing-objects"to the list of replication features specified to
mc replicate add --replicate.
For existing replication rules, add
"existing-objects"to the list of existing replication features using
mc replicate update --replicate. You must specify all desired replication features when editing the replication rule.
Enabling existing object replication does not increase the priority of objects pending replication. MinIO uses the same core replication scanner and queue system for detecting and synchronizing objects regardless of the enabled replication feature. The time required to fully synchronize a bucket depends on a number of factors, including but not limited to the current cluster replication load, overall cluster load, and the size of the namespace (all objects in the bucket).
If versioning was not previously enabled when configuring bucket replication,
existing objects have a
versionid = null. These objects do replicate.
MinIO existing object replication implements functionality similar to AWS: Replicating existing objects between S3 buckets without the overhead of contacting technical support.
Synchronous vs Asynchronous Replication
MinIO supports specifying either asynchronous (default) or synchronous replication for a given remote target.
With asynchronous replication, MinIO completes the originating
PUT operation before placing the object into a replication queue.
The originating client may therefore see a successful
PUT operation before the object is replicated.
While this may result in stale or missing objects on the remote, it mitigates the risk of slow write operations due to replication load.
With synchronous replication, MinIO attempts to replicate the object prior to completing the originating
MinIO returns a successful
PUT operation whether or not the replication attempt succeeds.
This reduces the risk of slow write operations at a possible cost of stale or missing objects on the remote location.
You must explicitly enable synchronous replication when configuring the remote
target target using the
mc admin bucket remote add command with the
This section documents internal replication behavior and is not critical to using or implementing replication. This documentation is provided strictly for learning and educational purposes.
MinIO uses a replication queuing system with multiple concurrent replication workers operating on that queue. MinIO continuously works to replicate and remove objects from the queue while scanning for new unreplicated objects to add to the queue.
MinIO queues failed replication operations and retries those operations until replication succeeds. This helps keep replication up-to-date without relying on the MinIO scanner to notice unreplicated object versions.
Changed in version RELEASE.2022-08-11T04-37-28Z: Failed or pending replications requeue automatically when performing a list or any
HEAD API method.
For example, using
mc cat, or
mc ls after a remote location comes back online requeues replication.
MinIO sets the
X-Amz-Replication-Status metadata field according to the
replication state of the object:
The object has not yet been replicated. MinIO applies this state
if the object meets one of the configured replication rules on the
bucket. MinIO continuously scans for
For multi-site replication, objects remain
The object has successfully replicated to the remote cluster.
The object failed to replicate to the remote cluster.
MinIO continuously scans for
The object is itself a replica from a remote source.
The replication process generally has one of the following flows:
PENDING -> COMPLETED
PENDING -> FAILED -> COMPLETED