Ceph: Designing and Implementing Scalable Storage Systems

LRC

One of the disadvantages of using erasure coding in a distributed storage system is that recovery can be very intensive on networking between hosts. As each shard is stored on a separate host, recovery operations require multiple hosts to participate in the process. When the CRUSH topology spans multiple racks, this can put pressure on the inter-rack networking links. The Locally Repairable erasure Code (LRC) erasure plugin adds an additional parity shard, which is local to each OSD node. This allows recovery operations to remain local to the node where an OSD has failed and remove the need for nodes to receive data from all other remaining shard-holding nodes.

However, the addition of these local recovery codes does impact the amount ...