BS ISO/IEC 20919:2021 - Page 4

Information technology. Linear tape file system (LTFS) Format specification. | Status: Current

2 Scope This document defines the LTFS Format requirements for interchanged media that claims LTFS compliance. Those requirements are specified as the size and sequence of data blocks and file marks on the media, the content and form of special data constructs (the LTFS Label and LTFS Index), and the content of the partition labels and use of MAM parameters. The data content (not the physical media) of the LTFS format shall be interchangeable among all data storage systems claiming conformance to this format. Physical media interchange is dependent on compatibility of physical media and the media access devices in use.

NOTE This document does not contain instructions or tape command sequences to build the LTFS structure.

2.1 Versions

This document describes version 2.5.0 of the Linear Tape File System (LTFS) Format Specification. The version number for the LTFS Format Specification consists of three integer elements separated by period characters of the form M.N.R, where M, N and R are positive integers or zero. Differences in the version number between different revisions of this specification indicate the nature of the changes made between the two revisions. Each of the integers in the format specification are incremented according to Table 1. Table 1 — Version elements Element Description M Incremented when a major update has been made to the LTFS Format Specification. Major updates are defined as any change to the on-media format or specification semantics that are expected to break compatibility with older versions of the specification. N Incremented when a minor update has been made to the LTFS Format Specification. Minor updates are defined as any change to the on-media format or specification semantics that is not expected to break compatibility with older versions of the specification that have the same value for M in the version number. R Incremented when textual revisions are made to the LTFS Format Specification. Textual revisions are defined as revisions that improve the clarity of the specification document without changing the intent of the document. By definition, minor changes do not alter the on-media format or specification semantics.

NOTE 1 When any element of the specification version number is incremented, all sub-ordinate elements to the right are reset to zero. For example, if the version is 1.0.12 and N is incremented to 1, then R is set to zero resulting in version 1.1.0.

NOTE 2 The first public version of this document used version number 1.0. This value should be interpreted as equivalent to 1.0.0 in the version numbering defined in this document.

The result of comparison between two LTFS version numbers MA.NA.RA and MB .NB .RB is defined in Table 2. Table 2 — ersion comparisons Conditional Description MA < MB MA.NA.RA is an earlier version than MB .NB .RB . MA = MB and MA < NB MA.NA.RA is an earlier version than MB .NB .RB . MA = MB and NA = NB and RA < RB MA.NA.RA is an earlier version than MB .NB .RB . However, as defined above, changes that result only in a different R value are descriptive changes in the specification rather than on media changes.