Binary Index and Journal Embedding in the Linear Tape File System

Abstract

Since its introduction the Linear Tape File System (LTFS) has made interoperable use of tape between different vendors and storage systems possible. The open standard allows files written to tape on one system to be moved to any other system that understands LTFS and easily retrieved without a vendor specific system. The format presents the tape as a hierarchical directory structure, allowing files to be organised into folders by keeping an index on-tape. In this paper we present an extended method of storing the LTFS index in binary form as well as a mechanism that embeds a binary recovery journal into the format, allowing an LTFS formatted volume to be recoverable in the event of power loss or other failure scenarios that would normally cause data loss. This is achieved while providing complete backward compatibility with existing LTFS tools and without violating or modifying the LTFS standard. Further, the binary form improves the space efficiency of the stored indices and improves handling of volumes with millions of files.