Publication Date

5-2010

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Computer Engineering

Department

Electrical and Computer Engineering

Supervisory Committee Chair

Sin Ming Loo, Ph.D.

Abstract

Flash memory can be found in media players, cameras, cell phones and portable storage. These consumer items have universally compatible storage devices. However, what is their longevity and what is the long-term data retention reliability? This thesis will explore and attempt to answer these questions. Predicting accurate endurance ratings and long-term storage reliability is problematic; a storage card in a cell phone will simply wear differently if used for personal computer backup. Advertised longevity ratings can also be ambiguous, specified in a number of years of ‘typical’ and ‘average’ use.

This thesis begins by exploring the operation of flash technology used in managed NAND devices. Operational and hidden byproducts of controlling flash memory were identified then directly observed on a sampled MultiMediaCard (MMC) card. The collected data was graphed to calculate the life span of the product for several synthetic data transfer categories. Combined with the total storage capacity, the factors used in longevity calculations are shown to be dependent upon the transfer method.

To answer the original question, a hypothetical camera file storage usage model was contrasted against measured wear data to calculate longevity. When changing the addressing randomness of writing data to fifty percent of total transfers, the 10-year advertised longevity was shown diminished by half. This demonstrated how data storage randomness of the usage model influences device longevity.

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