Ceph: Designing and Implementing Scalable Storage Systems

Alternative caching mechanisms

While the native RADOS tiering functionality provides numerous benefits around flexibility and allows management by the same Ceph toolset. However, it cannot be denied that for pure performance RADOS tiering lags behind other caching technologies that typically function at the block device level.

Bcache is a block device cache in the Linux kernel, which can use an SSD to cache a slower block device such as a spinning disk.

Bcache is one example of a popular way of increasing the performance of Ceph with SSDs. Unlike RADOS tiering, which you can choose which pool you wish to cache, with bcache the entire OSD is cached. This method of caching brings a number of advantages around performance. The first is that ...