Ceph is a distributed self healing block storage software. By default it keeps copies of objects to recover from the failure of a disk or a machine. But Ceph can also use Erasure Code to reduce the raw storage requirements while increasing the data durability. For instance three replicas requiring 300% raw storage can be reduced to 130% with Erasure Code. This benefit comes at a price: it uses more CPU and is less flexible than a simple replication. This presentation will explain the Erasure Code logic and its tradeoffs.
Dachary works as a developer on http://ceph.com with a focus on Erasure Code and the maintenance of stable releases.