Tape Filesystems TAR and LTFS

Aug 26, 2025

Overview
XenData Archive Series software supports two tape formats: its own extended TAR format and the LTFS format. This technote outlines the features and drawbacks of both, helping you make an informed choice based on your specific needs.

TAR Format

XenData’s original tape format is an extension of the Unix PAX/TAR format. XenData’s implementation writes an index to the tape when it becomes full allowing it to be moved from one XenData system to another without need to scan the entire tape. The XenData TAR format supports both rewritable and WORM LTO cartridges.

LTFS Format 

The LTFS format was introduced by IBM in 2010 alongside the LTO-5 tape generation. It was designed to support media interchange through a standardized approach and was widely adopted LTFS uses partitioned tape technology, storing a table of contents on an easily accessible index partition at the beginning of the tape. This allows systems to read the index quickly when tapes are transferred between systems, even when the managing software is from different companies. The LTFS format supports only rewritable LTO cartridges; it does not support WORM cartridges.

TAR Benefits

TAR performs better than LTFS when storing large numbers of small files. LTFS writes multiple indexes throughout the tape, each containing an XML listing of all current files. With thousands of files, these indexes can grow significantly, consuming tape space that would otherwise be used for data. Additionally, LTFS performance may degrade due to the frequent generation of large XML files during data writing.

LTFS Benefits

The primary advantage of LTFS is its wide adoption, which facilitates media interchange between different sites and systems. This format is ideal if you plan to send tapes off-site for third-party access. The partitioned structure allows the table of contents to be quickly read when the tape is loaded into a new system