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
Awarded Best Paper!


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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@inproceedings {202319,
author = {Ram Kesavan and Rohit Singh and Travis Grusecki and Yuvraj Patel},
title = {Algorithms and Data Structures for Efficient Free Space Reclamation in {WAFL}},
booktitle = {15th USENIX Conference on File and Storage Technologies (FAST 17)},
year = {2017},
isbn = {978-1-931971-36-2},
address = {Santa Clara, CA},
pages = {1--14},
url = {},
publisher = {USENIX Association},
month = feb

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