UC Santa Cruz

For three decades, Kryder’s Law correctly predicted an exponential increase in bit density on disk platters, leading to an exponential drop in cost per gigabyte. However, disk now is over 7 times as expensive as it would have been had Kryder’s law continued unchanged from 2010, and industry projections suggest that in 2020 the gap will reach 200 times. Entrenched expectations of the cost of storing data for the long-term are being disrupted because of slow storage density growth. We use an economic model of long-term storage to investigate the implications of this disruption, including a comparison of archives based upon traditional disk media with alternative media such as flash. Our model shows that archives based upon alternative media are surprisingly cost competitive with archives based upon traditional disk media over the long-term. We propose using Archival Flash for long-term data preservation, with the trade off between longer data retention period and lower write cycles.