Abstract:
In archival systems, storage media are often replaced much earlier than their expected service life in exchange for other benefits of new media, such as higher capacity, bandwidth, and input/output operations per second, or lower costs. In an era of decreasing media density growth rates, retiring media early by considering only short-term benefits while discarding potential long-term cost benefits could have a negative long-term impact on an archival system’s economics. To extend an archival system’s life, at low cost, while keeping the performance degradation low, we suggest extending media lifetime past manufacturer recommendations, as well as increasing the horizon for planning and provisioning future media purchases. We present a cost-benefit analysis of the impact of prolonged media usage and long-term planning. Through Monte Carlo simulation, we simulate the behavior of an archival system using tapes, hard disk drives (HDDs), solid state devices (SSDs), and Blu-ray discs. We show that leaving older media in the archival system makes economic sense for SSDs, without significantly affecting reliability; we show cost improvements of approximately 10% for SSDs for a low annual media density growth rate, such as 5%, which would have been a loss of 35%, for a high annual media density rate, such as 20%. We show that, for SSDs and hard disks, the optimal planning time of an archival system is at least as long as the media service life. Combining prolonged media usage with an extended planning horizon, i.e extended planning time on overly used media helped bring the costs down by 15% for a system using SSDs.
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