An update-aware storage system for low-locality update-intensive workloads

Abstract

Traditional storage systems provide a simple read/write interface, which is inadequate for low-locality update-intensive workloads because it limits the disk scheduling flexibility and results in inefficient use of buffer memory and raw disk bandwidth. This paper describes an update-aware disk access interface that allows applications to explicitly specify disk update requests and associate with such requests call-back functions that will be invoked when the requested disk blocks are brought into memory. Because call-back functions offer a continuation mechanism after retrieval of requested blocks, storage systems supporting this interface are given more flexibility in scheduling pending disk update requests. In particular, this interface enables a simple but effective technique called Batching mOdifications with Sequential Commit (BOSC), which greatly improves the sustained throughput of a storage system under low-locality update-intensive workloads. In addition, together with a space-efficient low-latency disk logging technique, BOSC is able to deliver the same durability guarantee as synchronous disk updates. Empirical measurements show that the random update throughput of a BOSC-based B+ tree is more than an order of magnitude higher than that of the same B+ tree implementation on a traditional storage system.

A scalable deduplication and garbage collection engine for incremental backup

“…To address the first problem, Sungem adopts the BOSC (Batched Operation and Sequential Commit) mechanism [19] to modify the on-disk P-array. More specifically, Sungem partitions the P-array into a set of chunks, and allocates a per-chunk queue for each such chunk.…”