Michael Richmond

The Linear Tape File System

While there are many financial and practical reasons to prefer tape storage over disk for various applications, the difficultly of using tape in a general way is a major inhibitor to its wider usage. We present a file system that takes advantage of a new generation of tape hardware to provide efficient access to tape using standard, familiar system tools and interfaces. The Linear Tape File System (LTFS) makes using tape as easy, flexible, portable, and intuitive as using other removable and sharable media, such as a USB drive.

Reflections on remote reflection

The Java programming language provides both reflection and remote method invocation: reflection allows a program to inspect itself and its runtime environment, remote method invocation allows methods to be invoked transparently across a network. Unfortunately, the standard Java implementations of reflection and remote method invocation are incompatible: programmers cannot reflect on a remote application. We describe how Java systems can be extended to support Remote Reflection transparently by extending the standard Java API. Remote reflection can support remote debuggers, performance monitors, programming environments, application component servers such as Enterprise JavaBeans, and any other Java system that can be distributed across a network.

An I/O scheduler for dual-partitioned tapes

For a long time, tapes have had a single logical partition that was efficiently operated by dedicated software in batch mode. Nowadays, after the introduction of the LTO 5 standard, tapes support logical partitioning and, with the arrival of the Linear Tape File System (LTFS), their contents are exposed through the file system interface as regular files and directories. As a consequence, tape medium can now be accessed by concurrent processes that may create files in parallel. This creates two potential problems: interleaved data blocks and expensive partition switches. This paper presents the design and implementation of Unified, an I/O scheduler for LTFS that addresses these problems. We observe the effectiveness of delayed writes on decreased file fragmentation and the reduction of partition switches with the use of buffering and of redundant file copies. We also find out that software-based read prefetching, commonly used to manage disk devices, does not improve read times on tapes, but rather introduces potential overhead. With the techniques described in this paper, the Unified scheduler allows tape operations to be performed close to the raw hardware speed.

File-based media workflows using ltfs tapes

While digital video cameras have existed for over two decades digital video cassettes are still the primary storage medium in professional video archives. One of the major inhibitors in the transition to file-based workflows and media archives is the lack of an affordable, portable and archive compatible storage medium for the vast amounts of content produced. We address this need by a) defining the Linear Tape File System (LTFS) tape format for storing files, file properties, hierarchical directories and extended attributes; b) building file system software that allows LTFS tapes to be used in the same way as portable storage devices and c) leveraging LTFS to create efficient file-based media workflows. In the exhibit we present LTFS on LTO-5 (Linear Tape Open, Gen 5) tapes. We demonstrate file-based workflows with storyboards, video proxies and partial video restore of MXF (Material Exchange Format) professional video content. LTFS on LTO-5 tape can be 20 times higher in capacity, 10 times faster and 40 times cheaper than digital video cassette media. Furthermore, it combines the benefits of tape-based and file-based workflows. The new tape format streamlines file-based production, from video capture and transport to long-term archive. The tape format and file system implementation are available as open source.

PowerPoint and complexity

Everyone talks about software bloat, feature creep and the ever-increasing complexity of software. Each new version of a software package adds in new features. Very rarely, features are removed. But what really happens as software evolves? This animated film illustrates the evolution of PowerPointover seven versions from 1987-2001. With each version the user has faced increasing application complexity. Knowing how software evolves is of increasing importance as we move to building ultra-large scale software and developing software in the context of software ecologies. This film uses abstract graphical representations of the application features and relationships between features. Time-lapse animation of these abstract representations are used to convey an understanding of how this application has evolved. This animation is based on data from a project that is mapping the user interface and application functionality available in every release of Microsoft PowerPoint for the Macintosh. To date this study spans 7 releases of this application.