The design and implementation of a log-structured file system
ACM Transactions on Computer Systems (TOCS)
ACM SIGOPS Operating Systems Review
A performance comparison of RAID-5 and log-structured arrays
HPDC '95 Proceedings of the 4th IEEE International Symposium on High Performance Distributed Computing
Algorithms and data structures for flash memories
ACM Computing Surveys (CSUR)
Efficient identification of hot data for flash memory storage systems
ACM Transactions on Storage (TOS)
Write off-loading: Practical power management for enterprise storage
ACM Transactions on Storage (TOS)
A class of mean field interaction models for computer and communication systems
Performance Evaluation
Write amplification analysis in flash-based solid state drives
SYSTOR '09 Proceedings of SYSTOR 2009: The Israeli Experimental Systems Conference
A survey of Flash Translation Layer
Journal of Systems Architecture: the EUROMICRO Journal
Proceedings of the eleventh international joint conference on Measurement and modeling of computer systems
SRCMap: energy proportional storage using dynamic consolidation
FAST'10 Proceedings of the 8th USENIX conference on File and storage technologies
Performance of greedy garbage collection in flash-based solid-state drives
Performance Evaluation
The bleak future of NAND flash memory
FAST'12 Proceedings of the 10th USENIX conference on File and Storage Technologies
SFS: random write considered harmful in solid state drives
FAST'12 Proceedings of the 10th USENIX conference on File and Storage Technologies
A process-aware hot/cold identification scheme for flash memory storage systems
IEEE Transactions on Consumer Electronics
Analytic modeling of SSD write performance
Proceedings of the 5th Annual International Systems and Storage Conference
Continuous approximation of collective system behaviour: A tutorial
Performance Evaluation
A mean field model for a class of garbage collection algorithms in flash-based solid state drives
Proceedings of the ACM SIGMETRICS/international conference on Measurement and modeling of computer systems
Proceedings of the ACM SIGMETRICS/international conference on Measurement and modeling of computer systems
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To avoid a poor random write performance, flash-based solid state drives typically rely on an internal log-structure. This log-structure reduces the write amplification and thereby improves the write throughput and extends the drive's lifespan. In this paper, we analyze the performance of the log-structure combined with the d-choices garbage collection algorithm, which repeatedly selects the block with the fewest number of valid pages out of a set of d randomly chosen blocks, and consider non-uniform random write workloads. Using a mean field model, we show that the write amplification worsens as the hot data gets hotter. Next, we introduce the double log-structure, which uses a separate log for internal and external write requests. Although the double log-structure performs identically to the single log-structure under uniform random writes, we show that it drastically reduces the write amplification of the d-choices algorithm in the presence of hot data. In other words, the double log-structure yields an automatic form of data separation. Further, with the double log-structure there exists an optimal value for d (typically around 10), meaning the greedy garbage collection algorithm is no longer optimal. Finally, both mean field models introduced in this paper are validated using simulation experiments.