How objects are stored (replication or erasure coding)
StorageGRID can protect objects against loss either by storing replicated copies or by storing erasure-coded copies. You specify the type of copies to create in the placement instructions of ILM rules.
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.
Why you should not use single-copy replication
When creating an ILM rule to create replicated copies, you should always specify at least two copies for any time period in the placement instructions.
What erasure coding is
Erasure coding is the second method used by StorageGRID to store object data. When StorageGRID matches objects to an ILM rule that is configured to create erasure-coded copies, it slices object data into data fragments, computes additional parity fragments, and stores each fragment on a different Storage Node. When an object is accessed, it is reassembled using the stored fragments. If a data or a parity fragment becomes corrupt or lost, the erasure coding algorithm can recreate that fragment using a subset of the remaining data and parity fragments.
What erasure coding schemes are
When you configure the Erasure Coding profile for an ILM rule, you select an available erasure coding scheme based on how many Storage Nodes and sites make up the storage pool you plan to use. Erasure coding schemes control how many data fragments and how many parity fragments are created for each object.
Advantages, disadvantages, and requirements for erasure coding
Before deciding whether to use replication or erasure coding to protect object data from loss, you should understand the advantages, disadvantages, and the requirements for erasure coding.