μCache: a mutable cache for SMR translation layer
2020 28th International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS)(2020)
摘要
Shingled Magnetic Recording (SMR) may be combined with conventional (re-writable) recording on the same drive; in host-managed drives shipping today this capability is used to provide a small number of re-writable zones, typically totaling a few tens of GB. Although these re-writable zones are widely used by SMR-aware applications, the literature to date has ignored them and focused on fully-shingled devices. We describe μCache, an SMR translation layer (STL) using re-writable (mutable) zones to take advantage of both workload spatial and temporal locality to reduce the garbage collection overhead resulted from out-of-place writes. In μCache the volume LBA space is divided into fixed -sized buckets and, on write access, the corresponding bucket is copied (promoted) to the re-writable zones, allowing subsequent writes to the same bucket be served in - place resulting in fewer garbage collection cycles. We evaluate μCache in simulation against real-world traces and show that with appropriate parameters it is able to hold the entire write working set of most workloads in re-writable storage, virtually eliminating garbage collection overhead. We also emulate μCache by replaying its translated traces against actual drive and show that 1) it outperforms its examined counterpart, an E-region based translation approach on average by 2x and up to 5.1x, and 2) it incurs additional latency only for a small fraction of write operations, (up to 10%) when compared with conventional non-shingled disks.
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关键词
shingled magnetic recording,translation layer
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