Edwin R. Childers

Six orders of magnitude in linear tape technology: The one-terabyte project

For the last 50 years, tape has persisted as the media of choice when inexpensive data storage is required and speed is not critical. The cost of tape storage normalized per unit capacity (dollars per gigabyte) decreased steadily over this time, driven primarily by advances in areal density and reduction of tape thickness. This paper reports the next advance in tape storage--a demonstration of a tenfold increase in capacity over current-generation Linear Tape-Open® (LTO®) systems. One terabyte (1 TB, or 1000 GB) of uncompressed data was written on half-inch tape using the LTO form factor. This technical breakthrough involves significant advances in nearly every aspect of the recording process: heads, media, channel electronics, and recording platform.

Seamlessly integrating disk and tape in a multi-tiered distributed file system

The explosion of data volumes in enterprise environments and limited budgets have triggered the need for multi-tiered storage systems. With the bulk of the data being extremely infrequently accessed, tape is a natural fit for storing such data. In this paper we present our approach to a file storage system that seamlessly integrates disk and tape, enabling a bottomless and cost-effective storage architecture that can scale to accommodate Big Data requirements. The proposed system offers access to data through a POSIX filesystem interface under a single global namespace, optimizing the placement of data across disk and tape tiers. Using a self-contained, standardized and open filesystem format on the removable tape media, the proposed system avoids dependence on proprietary software and external metadata servers to access the data stored on tape. By internally managing the tape tier resources, such as tape drives and cartridges, the system relieves the user from the burden of dealing with the complexities of tape storage. Our implementation, which is based on the GPFS and LTFS filesystems, demonstrates the applicability of the proposed architecture in real-world environments. Our experimental evaluation has shown that this is a very promising approach in terms scalability, performance and manageability. The proposed system has been productized by IBM as LTFS Enterprise Edition.