ISO/IEC 20919:2021

INTERNATIONAL ISO/IEC
STANDARD 20919
Second edition
2021-07
Information technology — Linear tape
file system (LTFS) Format specification
Technologies de l'information — Spécification du format de système
de fichier à bande magnétique
PROOF/ÉPREUVE
Reference number
ISO/IEC 20919:2021(E)
©
ISO/IEC 2021

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ISO/IEC 20919:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii PROOF/ÉPREUVE © ISO/IEC 2021 – All rights reserved

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ISO/IEC 20919:2021(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of document should be noted (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details
of any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent
declarations received (see patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
 www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by the Storage Networking Industry Association (SNIA) (as Linear Tape File
System (LTFS) Format Specification, Version 2.5) and drafted in accordance with its editorial rules. It was
adopted, under the JTC 1 PAS procedure, by Joint Technical Committee ISO/IEC JTC 1, Information
technology.
This second edition cancels and replaces the first edition (ISO/IEC 20919:2016), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— Volume Advisory Locking — a method of marking a volume as locked against future modification;
— Percent Encoding — method of including previously reserved characters in names of files and
directories;
— Incremental Indexes — a method of recording a smaller index containing only changes since the last
index;
— File hashes — a method of recording fils hash information in the index in an interchangeable manner;
— Open For Write — a method of noting files in the index which were still open at the time the index is
written to tape.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-
committees.
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ISO/IEC 20919:2021(E)

USAGE
Copyright © 2020 SNIA. All rights reserved. All other trademarks or registered trademarks are the
property of their respective owners.

The SNIA hereby grants permission for individuals to use this document for personal use only, and for
corporations and other business entities to use this document for internal use only (including internal
copying, distribution, and display) provided that:

1. Any text, diagram, chart, table or definition reproduced shall be reproduced in its entirety with
no alteration, and,

2. Any document, printed or electronic, in which material from this document (or any portion
hereof) is reproduced, shall acknowledge the SNIA copyright on that material, and shall credit
the SNIA for granting permission for its reuse.

Other than as explicitly provided above, you may not make any commercial use of this document or
any portion thereof, or distribute this document to third parties. All rights not explicitly granted are
expressly reserved to SNIA.

Permission to use this document for purposes other than those enumerated above may be requested
by e-mailing tcmd@snia.org. Please include the identity of the requesting individual and/or company
and a brief description of the purpose, nature, and scope of the requested use.

All code fragments, scripts, data tables, and sample code in this SNIA document are made available
under the following license:

BSD 3-Clause Software License

Copyright (c) 2020, The Storage Networking Industry Association.

Redistribution and use in source and binary forms, with or without modification, are
permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of
conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of
conditions and the following disclaimer in the documentation and/or other materials
provided with the distribution.

* Neither the name of The Storage Networking Industry Association (SNIA) nor the names
of its contributors may be used to endorse or promote products derived from this software
without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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ISO/IEC 20919:2021(E)


DISCLAIMER
The information contained in this publication is subject to change without notice. The SNIA makes no
warranty of any kind with regard to this specification, including, but not limited to, the implied
warranties of merchantability and fitness for a particular purpose. The SNIA shall not be liable for
errors contained herein or for incidental or consequential damages in connection with the furnishing,
performance, or use of this specification.

LTFS Format Specification SNIA Standard 3
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ISO/IEC 20919:2021(E)

Revision History

Revision Date Sections Originator Comments
2.3.0 rev 1 3/18/14 Add section F.3 SNIA LTFS TWG Edits during TWG F2F
2.3.0 rev 2 12/15/14 Add Changes per SNIA LTFS TWG Edits adding Volume Advisory
TWG Locking, Volume UUID and LTFS
Name Encoding
2.3.0 rev 3 3/18/15 Add changes per SNIA LTFS TWG Edits Advisory Locking,
TWG Sha512,Media Pool Extended
Attributes &MAM
2.3.0 rev 4 3/24/15 Add edits from SNIA LTFS TWG Cleanup some reference errors
TWG review and minor editorial changes
2.3.0 rev 5 9/15/15 Add example 3 to SNIA LTFS TWG Added additional description
Appendix F.1.6 and example to describe
reclamation of spanned file
segments
2.3.0 rev 6 9/15/15 Add edits from SNIA LTFS TWG Revised wording in Appendix
TWG review F.1.6 example 3
2.4.0 rev 0 11/14/15 Add work from SNIA LTFS TWG Added changes listed in Change
TWG history
2.4.0 rev 1 1/12/17 Add edits from SNIA LTFS TWG Cleaned up some hyperlinks
TWG review and minor editorial changes
2.4.0 rev 2 1/17/17 Add edits from SNIA LTFS TWG Minor editorial changes
TWG F2F
2.4.0 rev3 6/12/17 Add edits from SNIA LTFS TWG Added Advisory Locking
TWG changes
2.4.0 rev 4 6/13/17 Add Media Pool SNIA LTFS TWG Added additional extended
changes per TWG attributes for Media Pool
2.4.0 rev 5 6/19/17 Add edits per SNIA LTFS TWG Cleaned up a couple of
TWG typographical errors
2.4.0 rev 6 10/10/17 Add edits per SNIA LTFS TWG Incorporated public review
TWG editorial comments
2.4.0 rev 7 10/18/17 Add edits per SNIA LTFS TWG Minor editorial changes
TWG
2.4.0 rev 8 10/24/17 Annex G SNIA LTFS TWG Minor editorial change
2.4.0 rev 9 11/14/17 Annex G SNIA LTFS TWG Minor editorial change
2.5.0 rev 0 12/04/18 Sections 5 & 9, SNIA LTFS TWG Add incremental indexes;
Annex B, etc. changes for sync behavior
2.5.0 rev 1 02/11/19 Add Annex H; SNIA LTFS TWG New Annex describing
edits per TWG incremental indexes
2.5.0 rev 2 04/02/19 Section 9.2; SNIA LTFS TWG Corrected typos in example
Annex H XML, updated flowchart in
Annex H to clarify intent
2.5.1 rev 0 08/18/20 Section 3; SNIA LTFS TWG Editorial changes to References
Annex I per feedback from ISO
Suggestion for changes or modifications to this document should be sent to the SNIA Linear Tape File
System Technical Work Group at http://www.snia.org/feedback/.


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Changes between v1.0 and v2.0.0
• Incremented version number to 2.0.0 and updated date to March 11, 2011.
• Improvements in specification text to remove ambiguity and clarify intention of the specification.
These changes were made at several locations throughout the document.
• Improvements to clarify description of MAM parameters in Section 10 Medium Auxiliary Memory.
• Removed reference to a specific version of the Unicode standard in Section 7.5 Name pattern
format. This removes any requirement to use specific versions of Unicode support code in an
implementation.
• Improved description of Name pattern format to remove ambiguity in Section 7.5 Name pattern
format.
• Added description of LTFS Format specification version numbering in Section 2.1 Versions.
• Updated XML Schema for Label and Index to match version number format in Annex A and
Annex B.
• Added specification of minimum and recommended blocksize value for LTFS Volumes to Section
8.1.2 LTFS Label.
• Added definition of allowed version numbers to Section 8.1.2 LTFS Label and Section 9.2 Index.
• Added definition of fileoffset tag in Section 9.2 Index.
• Extended description in Section 6 Data Extents to support addition of fileoffset tag and associated
functionality.
• Added definition of highestfileuid tag in Section 9.2 Index.
• Added definition of fileuid tag in Section 9.2 Index.
• Added definition of backuptime tag in Section 9.2 Index.
• Incremented version number in Application Client Specific Information (ACSI) structure shown in
Section 10.3 Use of Volume Coherency Information for LTFS. This increment allows identification
of LTFS Volumes written with a LTFS v1.0 compliant implementation. A widely used v1.0
implementation wrote ambiguous ACSI values due to an implementation bug.
• Added definition of extended attributes in the ltfs.* namespace in Annex C.
• Added description for handling unknown XML tags in Index to Section 9.2.13 Managing LTFS
Indexes.
Changes between v2.0.0 and v2.0.1
• Incremented specification version number to 2.0.1.
• Updated specification date to August 17, 2011.
• Expanded historical record of changes between revisions of LTFS Format Specification.
• Improved description of constraints for two Indexes having the same generation number in
Section 5.4.1 Generation Number to make it clear that differences in access time values is
permitted between Indexes that are otherwise except for self pointer and index pointer values.
• Added note in Section 5.4.1 Generation Number to explicitly state that Index generation numbers
may increase by integer values other than 1.
• Expanded description of the ltfs.sync extended attribute in Annex C . The expanded description
explicitly states that this extended attribute triggers a sync of the in-memory data to the storage
media. That is, the operation is analogous to a POSIX sync operation.
Changes between v2.0.1 and v2.1.0
• Incremented specification version number to 2.1.0.
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ISO/IEC 20919:2021(E)

• Updated specification date to October 18, 2012.
• Added definition of symlink tag in Section 9.2 Index.
• Added example of symlink tag use in Annex E.
• Added symlink tag to Annex B.
• Added description of “ltfs.vendor.X.Y” extended attribute namespace in Annex C .
• Added description of software metadata section in Annex C.
• Added description of drive metadata section in Annex C.
• Added ”ltfs.labelVersion” extended attribute in Annex C.
• Added ”ltfs.indexVersion” extended attribute in Annex C
• Added ”ltfs.mediaEncrypted” extended attribute in Annex C .
• Improved description of ”ltfs.mediaStorageAlert” extended attribute in Annex C.
Changes between v2.1.0 and v2.2.0
• Incremented specification version number to 2.2.0.
• Updated specification date to July 16, 2013.
• Changed “2010” to “2013” in XML examples.
• Editorial Cleanup.
• Changed “extentinfo” definition in Section 9.2 Index.
• Changed “symlink” definition in Section 9.2 Index.
• Added additional paragraph to “symlink” definition in Section 9.2 Index.
• Added general comments at start of Section 10 Medium Auxiliary Memory.
• Added Section 10.4 Use of Host-type Attributes for LTFS.
• Removed Section 9 Certification from document.
• Added “ltfs.mamBarcode” extended attribute in Volume Metadata.
• Added “ltfs.mamApplicationVendor” extended attribute in Volume Metadata.
• Added “ltfs.mamApplicationVersion” extended attribute in Volume Metadata.
• Added “ltfs.mamApplicationFormatVersion” extended attribute in Volume Metadata.
• Added new Annex F Interoperability Recommendation and added File Spanning and File
Permissions subsections
Changes between v2.2.0 and 2.3.0 rev 1
• Add section F.3 Storing File Hash Values in LTFS
• Add Section 10.5 Volume Advisory Locking to Section 10 Medium Auxiliary Memory
• Added Volume UUID to Section 10.4 and Section 10.4.8
• Added LTFS Name Encoding to Sections 3.1, 7.4, 9.2.1 and 9.2.2
• Added SHA512 to Section F.3 Storing Hash Values in LTFS
• ISO document formatting changes
• Add Media Pool Extended Attributes and MAM

Changes between v2.3.0 rev 1 and v2.4.0
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• Incremented specification version number to 2.4.0.
• Added new text to Section 10.5 Volume Advisory Locking
• Added new text to Annex C.4 VolumeMetadata, ltfs.volumeLockState
• Added new text for “openforwrite” to Section 9.2.9
• Added new entry to the file element list in Annex B
• Added new descriptive text to Annex E
• Added new example file “partialfile.bin” to Annex E
• Updated the compliance statement to “version 2.4.0” in Section 7.4 Name Format
• Added new percentencoding text to Section 7.4 Name Format
• Removed percentencoding definition from Section 9.2.7
• Removed percentencoding definition from Section 9.2.9
• Added new text to symlink definition in Section 9.2.9
• Removed percentencoding paragraph(s) from Section 9.2.10
• Removed the percentencoded entry from the directory, file and extended attributes sections in
Annex B
• Changed the name definition in the directory section of Annex B
• Changed the name definition in the file section of Annex B
• Changed the symlink definition in the file section of Annex B
• Changed the key definition in the extendedattributes section of Annex B
• Added new NameType definition to Annex B
• Changed the entry for fileuid “10” in Annex E

Changes between v2.4.0 and v2.4.0 rev 1
• Incremented specification version number to 2.4.0 rev 1.
• Changed version from 2.3.0 to 2.4.0 in Section 2.1 Versions
• Changed version from 2.3.0 to 2.4.0 in Annex E
• Cleaned up some hyperlinks and minor editorial changes

Changes between v2.4.0 rev 1 and v2.4.0 rev 2
• Changed version from 2.3.0 to 2.4.0 throughout document except for Section 9.2.19
• Changed updatetime in Annex E to reflect correct date/time value for example shown
• Changed highestfileuid in Annex E to reflect correct value for example shown
• Changed lockType to locktype throughout document
• Changed NameType to nametype throughout document

Changes between v2.4.0 rev 2 and v2.4.0 rev 3
• Updated the definition of the volumeLockState virtual extended attribute in Section 10.5 and
Annex C.4
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Changes between v2.4.0 rev 3 and v2.4.0 rev 4
• Updated the definition of the Media Pool MAM attribute in Section 10.4 and Annex F.4.1.1
Changes between v2.4.0 rev 4 and v2.4.0 rev 5
• Fixed a couple of typographical errors
Changes between v2.4.0 rev 5 and v2.4.0 rev 6
• Corrections to Annex B – XML Schema
• Added Annex G – character representations
• Clarified in Section 7.4 that percent encoding does not apply to Table 13, and added reference to
Annex G
• Added two further IBM contributors to the Acknowledgements
Changes between v2.4.0 rev 6 and v2.4.0 rev 7
• Changed title and reference of table G.1 in Annex G – applies to 2.3 and later
• Added clarifying note for symlinks in Annex G
Changes between v2.4.0 rev 7 and v2.4.0 rev 8
• Changed column heading in tables G.1 and G.2 to “symlink target name”
• Improved wording of Note 3 in Annex G
Changes between v2.4.0 rev 8 and v2.4.0 rev 9
• Changed column heading in tables G.1 and G.2 to “File name, directory name, filename pattern”
• Added corresponding Note 4 in Annex G

Changes between v2.4.0 rev 9 and v2.5.0
• Incremented specification version number to 2.5.0.
• Added new text to describe Full and Incremental Indexes, in particular in 5.4 Index Layout and 9
Index Format.
• Added new virtual extended attributes related to Incremental Indexes in C.4.
• Specify required behavior in response to writing ltfs.commitMessage and ltfs.sync VEAs in
Annex C.

Changes between v2.5.0 rev 0 and v2.5.0 rev 1
• Added new informative Annex H describing background information on Incremental Indexes
• Editorial changes to clarify required vs optional elements in Incremental Indexes in 9 Index
Format.
• Clarified that the required behavior for ltfs.commitMessage and ltfs.sync applies only to
implementations supporting those VEAs.

Changes between v2.5.0 rev 1 and v2.5.0 rev 2
• Corrected typos in Incremental Indexes example XML in 9.2.2 and 9.2.12
• Corrected typos in Annex H and amended flowchart H.1 to clarify the intent

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ISO/IEC 20919:2021(E)


Changes between v2.5.0 rev 2 and v2.5.1 rev 0
• Moved informative references from Section 3 to new Annex I Bibliography
• Amended all references to SPC-3 / SPC-4 to SPC-5
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ISO/IEC 20919:2021(E)

Acknowledgements
The SNIA LTFS Technical Working Group, which developed and reviewed this specification, would
like to recognize the significant contributions made by the following members:

EMC Corporation. . Don Deel
Hewlett Packard Enterprise . Chris Martin
IBM. . David Pease
.................................................. ................ Ed Childers
.................................................. ................ Takeshi Ishimoto
.................................................. ................ Atsushi Abe
NetApp. . David Slik
Oracle Corporation. . Matthew Gaffney
................................................. ................. Carl Madison
Quantum Corporation. . Paul Stone
………………………………………………. Jim Wong
SNIA. . Arnold Jones


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ISO/IEC 20919:2021(E)

Contents
1 Introduction . 15
2 Scope . 16
2.1 Versions . 16
2.2 Conformance . 17
3 Normative references . 18
4 Definitions and Acronyms . 19
4.1 Definitions . 19
4.2 Acronyms . 21
5 Volume Layout . 22
5.1 LTFS Partitions . 22
5.2 LTFS Constructs . 22
5.3 Partition Layout . 23
5.4 Index Layout . 24
6 Data Extents . 27
6.1 Extent Lists . 27
6.2 Extents Illustrated . 27
6.3 Files Illustrated . 29
7 Data Formats . 32
7.1 Boolean format . 32
7.2 Creator format . 32
7.3 Extended attribute value format . 32
7.4 Name format . 32
7.5 Name pattern format . 34
7.6 String format . 34
7.7 Time stamp format . 34
7.8 UUID format . 35
8 Label Format . 36
8.1 Label Construct . 36
9 Index Format . 39
9.1 Index Construct . 39
9.2 Index . 39
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10 Medium Auxiliary Memory . 53
10.1 Volume Change Reference . 53
10.2 Volume Coherency Information . 54
10.3 Use of Volume Coherency Information for LTFS . 5433
10.4 Use of Host-type Attributes for LTFS . 55
10.5 Volume Advisory Locking . 57
Annex A (normative) LTFS Label XML Schema . 59
Annex B (normative) LTFS Index XML Schemas . 61
B.1 LTFS Full Index XML Schema . 61
B.2 LTFS Incremental Index XML Schema . 63
Annex C (normative) Reserved Extended Attribute definitions . 66
C.1 Software Metadata . 66
C.2 Drive Metadata . 66
C.3 Object Metadata . 66
C.4 Volume Metadata . 67
C.5 Media Metadata. 69
Annex D (informative) Example of Valid Simple Complete LTFS Volume . 72
Annex E (informative) Complete Example LTFS Full Index . 73
Annex F (normative) Interoperability Recommendations . 78
F.1 Spanning Files across Multiple Tape Volumes in LTFS . 78
F.2 File Permissions in LTFS . 83
F.3 Storing File Hash Values in LTFS . 86
F.4 LTFS Media Pools . 87
Annex G (informative) Charac
...