Long-term threats to secure archives
Proceedings of the second ACM workshop on Storage security and survivability
SafeStore: a durable and practical storage system
ATC'07 2007 USENIX Annual Technical Conference on Proceedings of the USENIX Annual Technical Conference
Higher reliability redundant disk arrays: Organization, operation, and coding
ACM Transactions on Storage (TOS)
Challenges to long term digital preservation a glimpse of the Italian experience
DSP'09 Proceedings of the 16th international conference on Digital Signal Processing
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As disk drives have dropped in price relative to tape, the desire for the convenience and speed of online access to large data repositories has led to the deployment of petabyte-scale disk farms with thousands of disks. Unfortunately, the very large size of these repositories renders them vulnerable to previously rare failure modes such as multiple, unrelated disk failures leading to data loss. While some business models, such as free email servers, may be able to tolerate some occurrence of data loss, others, including premium online services and storage of simulation results at a national laboratory, cannot. This paper describes the effect of infant mortality on long-term failure rates of systems that must preserve their data for decades. Our failure models incorporate the well-known bathtub curve, which reflects the higher failure rates of new disk drives, a lower, constant failure rate during the remainder of the design life span, and increased failure rates as components wear out. Large systems are vulnerable to the "cohort effect" that occurs when many disks are simultaneously replaced by new disks. Our more accurate disk models and simulations have yielded predictions of system lifetimes that are more pessimistic than existing models that assume a constant disk failure rate. Thus, larger system scale requires designers to take disk infant mortality into account.