Increasing SSD Endurance for Enterprise Applications

Authors:Mohan, Vidyabhushan, Department of Computer ScienceUniversity of Virginia Sankar, Sriram, Department of Computer ScienceUniversity of Virginia Gurumurthi, Sudhanva, Department of Computer ScienceUniversity of Virginia

NAND flash based Solid State Disks (SSDs) are fast becoming the choice of primary storage replac- ing the traditional Hard Disk Drive (HDD) based storage media. The power and performance benefits of SSDs over HDDs are especially attractive for use in data centers, whose workloads are I/O intensive. However, the limited lifetime of SSDs is often cited as an obstacle in adopting them for data centers. One aspect of NAND flash memory reliability that significantly hinders the adoption of SSDs in data centers is write endurance. In order to study this limitation and suggest solutions to overcome this limitation, we have built a reliability model framework called FENCE to study flash memory reliability. FENCE captures the time-dependent property of write endurance and data retention of NAND flash memory by taking into account both the stress and recovery effects on NAND flash memory cells. Using FENCE, we analyze the tradeoffs between write endurance and data retention for both SLC and MLC flash. We make a case for increasing the endurance of MLC based SSDs by trading off their data retention property. We illustrate some refresh policies that can be applied to ensure data integrity of SSDs and suggest changes to the design of flash memory controller to support these refresh operations.

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Source Citation:

Mohan, Vidyabhushan, Sriram Sankar, and Sudhanva Gurumurthi. "Increasing SSD Endurance for Enterprise Applications." University of Virginia Dept. of Computer Science Tech Report (2011).

University of Virginia, Department of Computer Science
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