What replication is

Replication is one of two methods used by StorageGRID to store object data. When StorageGRID matches objects to an ILM rule that is configured to create replicated copies, the system creates exact copies of object data and stores the copies on Storage Nodes or Archive Nodes.

When you configure an ILM rule to create replicated copies, you specify how many copies should be created, where those copies should be placed, and how long the copies should be stored at each location.

In the following example, the ILM rule specifies that two replicated copies of each object be placed in a storage pool that contains three Storage Nodes.

Make 2 Copies rule

When StorageGRID matches objects to this rule, it creates two copies of the object, placing each copy on a different Storage Node in the storage pool. The two copies might be placed on any two of the three available Storage Nodes. In this case, the rule placed object copies on Storage Nodes 2 and 3. Because there are two copies, the object can be retrieved if any of the nodes in the storage pool fails.

Attention: In general, do not configure ILM rules to create only one replicated copy. If the only replicated copy is lost or corrupt, data will be lost. In addition, you might lose access to the object during maintenance or recovery operations. Use ILM to create a single replicated copy only if you are willing to risk the loss of object data when a failure occurs.
Note: StorageGRID can store only one replicated copy of an object on any given Storage Node. If your grid includes three Storage Nodes and you create a 4-copy ILM rule, only three copies will be made—one copy for each Storage Node.