Site Replication Overview

Site replication configures multiple independent MinIO deployments as a cluster of replicas called peer sites.

Site replication assumes the use of either the included MinIO identity provider (IDP) or an external IDP. All configured deployments must use the same IDP. Deployments using an external IDP must use the same configuration across sites.

For more information on site replication architecture and deployment concepts, see Deployment Architecture: Replicated MinIO Deployments.

MinIO does not recommend using MacOS, Windows, or non-orchestrated Containerized deployments for site replication outside of early development, evaluation, or general experimentation. For production, use Linux or Kubernetes

Overview

What Replicates Across All Sites

Each MinIO deployment (“peer site”) synchronizes the following changes across the other peer sites:

• Creation, modification, and deletion of buckets and objects, including

  • Bucket and Object Configurations
  • Policies
  • mc tag set
  • Locks, including retention and legal hold configurations
  • Encryption settings

• Creation and deletion of IAM users, groups, policies, and policy mappings to users or groups (for LDAP users or groups)

• Creation of Security Token Service (STS) credentials for session tokens verifiable from the local root credentials

• Creation and deletion of access keys (except those owned by the root user)

Site replication enables bucket versioning for all new and existing buckets on all replicated sites.

You can choose to replicate ILM expiration rules across peer sites. For new site replication configurations, use the mc admin replicate add with the --replicate-ilm-expiry flag. For existing site replication configurations, you can enable or disable the behavior using mc admin replicate update with either the --enable-ilm-expiry-replication or --disable-ilm-expiry-replication flag, as appropriate.

What Does Not Replicate Across Sites

MinIO deployments in a site replication configuration do not replicate the creation or modification of the following items:

• Bucket notifications
• Lifecycle management (ILM) configurations
• Site configuration settings

Initial Site Replication Process

After enabling site replication, identity and access management (IAM) settings sync in the following order:

• MinIO IDP
• OIDC
• LDAP

After the initial synchronization of data across peer sites, MinIO continually replicates and synchronizes replicable data among all sites as they occur on any site.

Site Healing

Any MinIO deployment in the site replication configuration can resynchronize damaged replica-eligible data from the peer with the most updated (“latest”) version of that data.

You can adjust how MinIO balances the scanner performance with read/write operations using either the MINIO_SCANNER_SPEED environment variable or the scanner speed configuration setting.

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 PUT operation. 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.

MinIO strongly recommends using the default asynchronous site replication. Synchronous site replication performance depends strongly on latency between sites, where higher latency can result in lower PUT performance and replication lag. To configure synchronous site replication use mc admin replicate update with the --mode option.

Proxy to Other Sites

MinIO peer sites can proxy GET/HEAD requests for an object to other peers to check if it exists. This allows a site that is healing or lagging behind other peers to still return an object persisted to other sites.

For example:

1. A client issues GET("data/invoices/january.xls") to Site1
2. Site1 cannot locate the object
3. Site1 proxies the request to Site2
4. Site2 returns the latest version of the requested object
5. Site1 returns the proxied object to the client

For GET/HEAD requests that do not include a unique version ID, the proxy request returns the latest version of that object on the peer site. This may result in retrieval of a non-current version of an object, such as if the responding peer site is also experiencing replication lag.

MinIO does not proxy LIST, DELETE, and PUT operations.

Prerequisites

Back Up Cluster Settings First

Use the mc admin cluster bucket export and mc admin cluster iam export commands to take a snapshot of the bucket metadata and IAM configurations respectively prior to configuring Site Replication. You can use these snapshots to restore bucket/IAM settings in the event of misconfiguration during site replication configuration.

One Site with Data at Setup

Only one site can have data at the time of setup. The other sites must be empty of buckets and objects.

After configuring site replication, any data on the first deployment replicates to the other sites.

All Sites Must Use the Same IDP

All sites must use the same Identity Provider. Site replication supports the included MinIO IDP, OIDC, or LDAP.

All Sites Must use the Same MinIO Server Version

All sites must have a matching and consistent MinIO Server version. Configuring replication between sites with mismatched MinIO Server versions may result in unexpected or undesired replication behavior.

You should also ensure the mc version used to configure replication closely matches the server version.

Access to the Same Encryption Service

For SSE-S3 or SSE-KMS encryption via Key Management Service (KMS), all sites must have access to a central KMS deployment.

You can achieve this with a central KES server or multiple KES servers (say one per site) connected via a central supported key vault server.

Replication Requires Versioning

Site replication requires Bucket Versioning and enables it for all created buckets automatically. You cannot disable versioning in site replication deployments.

MinIO cannot replicate objects in prefixes in the bucket that you excluded from versioning.

Load Balancers Installed on Each Site

Specify the URL or IP address of the site’s load balancer, reverse proxy, or similar network control plane component. Requests are automatically routed to nodes in the deployment.

MinIO recommends against using a single node hostname for a peer site. This creates a single point of failure: if that node goes offline, replication fails.

Switch to Site Replication from Bucket Replication

Bucket replication and multi-site replication are mutually exclusive. You cannot use both replication methods on the same deployments.

If you previously set up bucket replication and wish to now use site replication, you must first delete all of the bucket replication rules on the deployment that has data when initializing site replication. Use mc replicate rm on the command line to remove bucket replication rules.

Only one site can have data when setting up site replication. All other sites must be empty.

Tutorials

Configure Site Replication

The following steps create a new site replication configuration for three distributed deployments. One of the sites contains replicable data.

The three sites use aliases, minio1, minio2, and minio3, and only minio1 contains any data.

1. Deploy three or more separate MinIO sites, using the same IDP

   Start with empty sites or have no more than one site with any replicable data.

2. Configure an alias for each site

   Specify the URL or IP address of the site’s load balancer, reverse proxy, or similar network control plane component. Requests are automatically routed to nodes in the deployment.

   MinIO recommends against using a single node hostname for a peer site. This creates a single point of failure: if that node goes offline, replication fails.

   For example, for three MinIO sites, you might create aliases minio1, minio2, and minio3.

   Use mc alias set to define the hostname or IP of the load balancer managing connections to the site.

   mc alias set minio1 https://minio1.example.com:9000 adminuser adminpassword
   mc alias set minio2 https://minio2.example.com:9000 adminuser adminpassword
   mc alias set minio3 https://minio3.example.com:9000 adminuser adminpassword
   

   or define environment variables

   export MC_HOST_minio1=https://adminuser:adminpassword@minio1.example.com
   export MC_HOST_minio2=https://adminuser:adminpassword@minio2.example.com
   export MC_HOST_minio3=https://adminuser:adminpassword@minio3.example.com
   

3. Add site replication configuration

   mc admin replicate add minio1 minio2 minio3
   

   If all sites are empty, the order of the aliases does not matter. If one of the sites contains any replicable data, you must list it first.

   No more than one site can contain any replicable data.

4. Query the site replication configuration to verify

   mc admin replicate info minio1
   

   You can use the alias for any peer site in the site replication configuration.

5. Query the site replication status to confirm any initial data has replicated to all peer sites.

   mc admin replicate status minio1
   

   You can use the alias for any of the peer sites in the site replication configuration. The output should say that all replicable data is in sync.

   The output could resemble the following:

   Bucket replication status:
   ●  1/1 Buckets in sync
   
   Policy replication status:
   ●  5/5 Policies in sync
   
   User replication status:
   No Users present
   
   Group replication status:
   No Groups present
   

   For more on reviewing site replication, see the Site Replication Status tutorial.

Expand Site Replication

You can add more sites to an existing site replication configuration.

The new site must meet the following requirements:

• Site is fully deployed and accessible by hostname or IP
• Shares the IDP configuration as all other sites in the configuration
• Uses the same root user credentials as other configured sites
• Contains no bucket or object data

1. Deploy the new MinIO peer site(s) following the stated requirements

2. Configure an alias for the new site

   Specify the URL or IP address of the site’s load balancer, reverse proxy, or similar network control plane component. Requests are automatically routed to nodes in the deployment.

   MinIO recommends against using a single node hostname for a peer site. This creates a single point of failure: if that node goes offline, replication fails.

   To check the existing aliases, use mc alias list.

   Use mc alias set to define the hostname or IP of the load balancer managing connections to the new site(s).

   mc alias set minio4 https://minio4.example.com:9000 adminuser adminpassword
   

   or define environment variables

   export MC_HOST_minio4=https://adminuser:adminpassword@minio4.example.com
   

3. Add site replication configuration

   Use the mc admin replicate add command to expand the site replication configuration with the new peer site. Specify the alias of all existing peer sites, then the alias of the new site to add.

   For example, the following command adds the new peer site minio4 to an existing site replication configuration that includes the existing sites minio1, minio2, and minio3.

   mc admin replicate add minio1 minio2 minio3 minio4
   

   Note

   If any of the sites are unreachable or permanently lost, you must first remove the unreachable site(s) with mc admin replicate rm before expanding with the new site.

4. Query the site replication configuration to verify

   mc admin replicate info minio1
   

Modify a Site’s Endpoint

If a peer site changes its hostname, you can modify the replication configuration to reflect the new hostname.

1. Obtain the site’s Deployment ID with mc admin replicate info

   mc admin replicate info <ALIAS>
   

2. Update the site’s endpoint with mc admin replicate update

   mc admin replicate update ALIAS --deployment-id [DEPLOYMENT-ID] --endpoint [NEW-ENDPOINT]
   

   Replace [DEPLOYMENT-ID] with the deployment ID of the site to update.

   Replace [NEW-ENDPOINT] with the new endpoint for the site.

   Specify the URL or IP address of the site’s load balancer, reverse proxy, or similar network control plane component. Requests are automatically routed to nodes in the deployment.

   MinIO recommends against using a single node hostname for a peer site. This creates a single point of failure: if that node goes offline, replication fails.

Remove a Site from Replication

You can remove a site from replication at any time. You can re-add the site at a later date, but you must first completely wipe bucket and object data from the site.

Use mc admin replicate rm:

mc admin replicate rm ALIAS PEER_TO_REMOVE --force

• Replace ALIAS with the alias of any peer site in the replication configuration.
• Replace PEER_TO_REMOVE with the alias of the peer site to remove.

All healthy peers in the site replication configuration update to remove the specified peer automatically.

MinIO requires the --force flag to remove the peer from the site replication configuration.

Review Replication Status

MinIO provides information on replication across the sites for users, groups, policies, or buckets.

The summary information includes the number of Synced and Failed items for each category.

Use mc admin replicate status:

mc admin replicate status <ALIAS> --<flag> <value>

For example:

• mc admin replicate status minio3 --bucket images

  Displays the replication status for the images bucket on the minio3 site.

  The output resembles the following:

  ●  Bucket config replication summary for: images
  
  Bucket          | MINIO2          | MINIO3          | MINIO4
  Tags            |                 |                 |
  Policy          |                 |                 |
  Quota           |                 |                 |
  Retention       |                 |                 |
  Encryption      |                 |                 |
  Replication     | ✔               | ✔               | ✔
  

• mc admin replicate status minio3 --all

  Displays the replication status summary for all replication sites of which minio3 is part.

  The output resembles the following:

  Bucket replication status:
  ●  1/1 Buckets in sync
  
  Policy replication status:
  ●  5/5 Policies in sync
  
  User replication status:
  ●  1/1 Users in sync
  
  Group replication status:
  ●  0/2 Groups in sync
  
  Group           | MINIO2          | MINIO3          | MINIO4
  ittechs         | ✗  in-sync      |                 | ✗  in-sync
  managers        | ✗  in-sync      |                 | ✗  in-sync