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


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


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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@inproceedings {202251,
author = {Harendra Kumar and Yuvraj Patel and Ram Kesavan and Sumith Makam},
title = {High Performance Metadata Integrity Protection in the {WAFL} Copy-on-Write File System},
booktitle = {15th {USENIX} Conference on File and Storage Technologies ({FAST} 17)},
year = {2017},
isbn = {978-1-931971-36-2},
address = {Santa Clara, CA},
pages = {197--212},
url = {https://www.usenix.org/conference/fast17/technical-sessions/presentation/kumar},
publisher = {{USENIX} Association},