Caveat-Scriptor: Write Anywhere Shingled Disks

Proc. Of the Seventh USENIX Workshop on Hot Topics in Storage and File Systems (HotStorage’15), Santa Clara, CA, July 2015. Expanded paper available: Carnegie Mellon University Parallel Data Lab Technical Report CMU-PDL-15-101.

Saurabh Kadekodi, Swapnil Pimpale, Garth A. Gibson

Carnegie Mellon University
Pittsburgh, PA 15213


The increasing ubiquity of NAND flash storage is forcing magnetic disks to accelerate the rate at which they lower price per stored bit. Magnetic recording technologists have begun to pack tracks so closely that writing one track cannot avoid disturbing the information stored in adjacent tracks [13]. Specifically, the downstream track will be at least partially overwritten, or shingled by each write, as shown in Figure 1, and the upstream track will tolerate only a limited number of adjacent writes. Some data that was stored in the downstream track will be lost, forcing firmware or software to ensure that there was no data in those locations that might be read in the future.





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