Tag Archives: fast17

On the Accuracy and Scalability of Intensive I/O Workload Replay

Alireza Haghdoost and Weiping He, University of Minnesota; Jerry Fredin, NetApp; David H.C. Du, University of Minnesota

15th USENIX Conference on File and Storage Technologies (FAST 2017)
Feb. 27 – March 2, 2017 Santa Clara, CA

We introduce a replay tool that can be used to replay captured I/O workloads for performance evaluation of high-performance storage systems. We study several sources in the stock operating system that introduce the uncertainty of replaying a workload. Based on the remedies of these findings, we design and develop a new replay tool called hfplayer that can more accurately replay intensive block I/O workloads in a similar unscaled environment. However, to replay a given workload trace in a scaled environment, the dependency between I/O requests becomes crucial. Therefore, we propose a heuristic way of speculating I/O dependencies in a block I/O trace. Using the generated dependency graph, hfplayer is capable of replaying the I/O workload in a scaled environment. We evaluate hfplayer with a wide range of workloads using several accuracy metrics and find that it produces better accuracy when compared with two exiting available replay tools.

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High Performance Metadata Integrity Protection in the WAFL Copy-on-Write File System

Harendra Kumar; Yuvraj Patel, University of Wisconsin—Madison; Ram Kesavan and Sumith Makam, NetApp

15th USENIX Conference on File and Storage Technologies (FAST 2017)
Feb. 27 – March 2, 2017 Santa Clara, CA

We introduce a low-cost incremental checksum technique that protects metadata blocks against in-memory scribbles, and a lightweight digest-based transaction auditing mechanism that enforces file system consistency invariants. Compared with previous work, our techniques reduce performance overhead by an order of magnitude. They also help distinguish scribbles from logic bugs. We also present a mechanism to pinpoint the cause of scribbles on production systems. Our techniques have been productized in the NetApp® WAFL® (Write Anywhere File Layout) file system with negligible performance overhead, greatly reducing corruption-related incidents over the past five years, based on millions of runtime hours.

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Algorithms and Data Structures for Efficient Free Space Reclamation in WAFL

Ram Kesavan, Rohit Singh, and Travis Grusecki, NetApp; Yuvraj Patel, University of Wisconsin—Madison

15th USENIX Conference on File and Storage Technologies (FAST 2017)
Feb. 27 – March 2, 2017 Santa Clara, CA

NetApp®WAFL®is a transactional file system that uses the copy-on-write mechanism to support fast write performance and efficient snapshot creation. However, copy-on-write increases the demand on the file system to find free blocks quickly; failure to do so may impede allocations for incoming writes. Efficiency is also important, because the task may consume CPU and other resources. In this paper, we describe the evolution (over more than a decade) of WAFL’s algorithms and data structures for reclaiming space with minimal impact on the overall storage appliance performance.

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