Extending SSD lifetimes with disk-based write caches

TLDR

HDDs can match mid‑range SSDs’ sequential write bandwidth, and many workloads contain a significant fraction of block overwrites. The paper introduces Griffin, a hybrid storage device that uses an HDD as a write cache for an SSD. Griffin maintains a log‑structured HDD cache and periodically migrates cached data to reduce SSD writes while preserving performance. Evaluation on Windows I/O traces shows Griffin doubles SSD lifetime and cuts average I/O latency by 56%.

Abstract

We present Griffin, a hybrid storage device that uses a hard disk drive (HDD) as a write cache for a Solid State Device (SSD). Griffin is motivated by two observations: First, HDDs can match the sequential write bandwidth of mid-range SSDs. Second, both server and desktop workloads contain a significant fraction of block overwrites. By maintaining a log-structured HDD cache and migrating cached data periodically, Griffin reduces writes to the SSD while retaining its excellent performance. We evaluate Griffin using a variety of I/O traces from Windows systems and show that it extends SSD lifetime by a factor of two and reduces average I/O latency by 56%.