Cost of Tape versus Disk for Archival Storage

For archiving large datasets in high-performance computing facilities, tape technology has a long history of providing inexpensive capacity. However, as the memory-size of supercomputers continues to grow geometrically, the cost of tape bandwidth is becoming more important. The projected costs for tape-drives, robotics, and maintenance, are creating challenges for tape-based archives. The advent of erasure-coded object storage, driven by the "cloud storage" industry, might make it practical to implement archives using disks, or hybrid disk-and-tape systems. We used linear optimization techniques to investigate when and how this transition might best be made, taking into consideration our significant investment in tape technology. Our models introduce a technique to systematically relax constraints on the relationship between tape-capacity and tape-bandwidth, which governs a trade-off between cost and performance. We ran parameter studies that support some preliminary conclusions about paths forward for archive infrastructure at LANL.