Design, Implementation, and Evaluation of Write-Back Policy with Cache Augmented Data Stores

The Cache Augmented Data Store (CADS) architecture extends a persistent data store with an in-memory cache manager. It is widely deployed to support read-intensive workloads. However, its write-around and write-through policies prevent the caching tier from absorbing write load. This means the data store layer must scale to process writes even when the extra capacity is not needed for read load. We address this limitation by devising a write-back technique to enable the caching layer to process both reads and writes. This technique preserves ACID transactions. We present a client side implementation of write-back and evaluate it using the YCSB, BG, and TPC-C benchmarks. In addition, we compare our write-back with (a) write-back policy of a data store such as MongoDB and (b) write-back policy of a host-side cache such as Flashcache.