Linear Tape File System (LTFS) Media Format

Beginning with StorNext 5, users with LTO5/LTO6 tape media can choose to store archive copies to the traditional native StorNext tape format (ANTF) and/or to the new Open LTFS tape format.

Note: LTO7 tape media may be used with StorNext 5 release 5.4.0 (and later).

The new LTFS tape format offers most of the same StorNext 5 functionality as the existing ANTF format with the additional benefit of being portable. That is, tape media written in LTFS format by StorNext 5 can be vaulted and removed from the StorNext Storage Manager system and mounted elsewhere using the freely available Open LTFS package, allowing access to the data without requiring any additional software from Quantum.

The StorNext 5 implementation for LTFS is based on the Open LTFS Format Specification v2.0.0 and is compatible with implementations from other vendors at or above this version. The initial StorNext 5 implementation only supports LTFS on LTO5 and LTO6 tape media.

Note: StorNext 5 release 5.4.0 (and later) uses Open LTFS Format Specification v2.2.1 and supports LTO7 tape media.

Supported Features

StorNext 5 for LTFS includes support for the following features:

Policy-class-copy steering by media format type for LTO tape media
Automatic media selection and formatting
Distributed data-mover support
File versioning on LTFS media
File recovery from LTFS media
LTFS media defragmentation
Tape-to-tape copy from ANTF or LTFS to ANTF or LTFS formats
LTO7 media with StorNext 5 release 5.4.0 (or later)

Features Not Supported

Features NOT supported in StorNext 5 for LTFS:

Segmented files
LTFS volume spanning
StorNext backup to LTFS
Import of native LTFS media into StorNext
Export/import of StorNext managed LTFS media
LTO7 media prior to StorNext 5 release 5.4.0

Accessing StorNext-generated LTFS Media

Access of StorNext-generated LTFS media outside of StorNext (for example, by an Open LTFS package,) should be considered read-only.

A StorNext-generated LTFS medium may be rendered unusable within StorNext 5 if it is modified outside of StorNext 5. If the medium is required for data retrieval of truncated files within the StorNext file system, access to those files may not be possible if the medium is modified outside of StorNext.

Configuration Considerations

Now that two different media formats (ANTF/LTFS) are supported for LTO media in StorNext 5, certain items should be considered for configuration and usage so that StorNext users can make the best choices for their environment.

Following is a list of these items to consider:

StorNext Storage Manager LTFS support is based on LTFS Format Specification v2.0.0. The LTFS Format Specification does not support backwards compatibility with earlier versions of the specification.
The LTFS Format Specifications v2.0.0 and v2.2.1 are compatible with each other. If a tape is formatted with version v2.0.0 and is written by StorNext 5 release 5.4.0, the tape format will be upgraded to v2.2.1. Similarly, a tape formatted with version v2.2.1 will be downgraded to a v2.0.0 if it is written by StorNext 5 prior to release 5.4.0.
Neither LTFS Format v2.0.0 or v2.2.1 provide a means for maintaining file ownership and permissions when storing files to LTFS media. Instead, this is managed at LTFS file system mount time using options passed to the Open LTFS package commands. When used within StorNext Storage manager, access is restricted to user root and is not accessible outside of the StorNext Storage Manager processes. When mounted outside of StorNext Storage Manager, care should be taken to ensure proper access permissions are used when the LTFS volume is mounted.
Storage Manager does not support segmented files LTFS. This includes files being stored as well as files being copied from tape to tape (fsfilecopy/fsmedcopy). As a means to manage this, the configuration parameter DEF_MED_SPC_LTO_LTFS in file /usr/adic/TSM/config/fs_sysparm specifies the maximum file size that can be stored to LTFS media.
StorNext 5 supports a maximum tape block size of 1MB for LTFS. As a means to manage this, the configuration parameter FS_LTO_LTFS_BLOCK_FACTOR in file /usr/adic/TSM/config/fs_sysparm is used to calculate the LTFS tape block size and limit it to 1MB for LTFS formatted media.
LTFS allocates at least one tape block for each file, and no two files share the same tape block. Therefore, every file consumes an amount of space on tape that is a multiple of the tape block size. As a consequence, very small files do not make efficient use of tape capacity, especially when large tape block sizes are configured.
StorNext import of native LTFS media is not supported (that is, media that has been formatted and written to outside of StorNext Storage Manager).
Also, StorNext import of StorNext LTFS media is not supported between different installations of Storage Manager.
StorNext Backup (_adic_backup policy class) is not supported for LTFS.
Since LTFS is a file system on a tape, additional overhead is incurred when Storage Manager processes have to mount and unmount the LTFS file system. Because of this, ANTF will outperform LTFS in situations where small numbers of files and/or small amounts of data need to be stored, retrieved, or copied. Therefore, StorNext users will NOT want to configure LTFS for the primary copy used for file retrieval (for example, copy 1).
In order to minimize this additional overhead, system parameters should be configured to process high file counts and high byte counts for store and retrieve requests. The configuration parameter MAX_FILES_PER_CLUSTER in file /usr/adic/TSM/config/fs_sysparm should remain at the default of 3000 and not be reduced. The undocumented configuration parameter FS_CLUSTER_LIMIT_LTO in file /usr/adic/TSM/config/fs_sysparm should be increased to 1,000,000,000,000 (1TB) for LTO5 media, 2,000,000,000,000 (2TB) for LTO6 media, and 6,000,000,000,000 (6TB) for LTO7 media. The FS_CLUSTER_LIMIT_LTO parameter should be set to the lowest recommended LTO generation value in environments where multiple LTO generations are being used with LTFS.
The amount of meta data stored in the LTFS index partition grows as files are added to an LTFS volume. This meta data is always loaded into the fs_fmover process memory when the LTFS volume is mounted, and continues to grow as files are added to the LTFS volume. Therefore, it is expected behavior that the fs_fmover process memory requirements are larger when the source and/or destination media format type is LTFS as compared to when the source and destination media format types are both ANTF.
The LTFS standard prohibits the use of the following characters in either directory or file names:

: /
Attempting to store files to LTFS that have prohibited characters in either directory or file names in the path will fail and cause an admin alert to be generated. These files will then be removed from the store policy candidate list by having the FS_NO_STORE flag set in the file attributes. In order to successfully store these files, they must be renamed such that they no longer contain any prohibited characters in any of the directory or file names in the path. Once renamed, the FS_NO_STORE attribute flag must then be cleared using the fschfiat -sp command or the Tools > File and Directory Actions > Modify File Attributes GUI page in order for policy to place it back on the store candidate list. Future file modifications will be ignored and no additional copies will be made regardless of media type or format until the FS_NO_STORE attribute flag had been cleared. It is also strongly recommended to avoid using certain characters for interoperability between operating systems. The following characters should NOT be used in either directory or file names if the files are to be stored to LTFS media:

* ? < > " | \
While not prohibited on Linux or OS X, these characters cannot be used on Windows because of additional restrictions for characters used in directory and file names.

In the Steering tab in the Storage Manager Policies configuration page, you can select from the Media Format list, either ANTF or LTFS formats for the LTO (tape) Media Type.

Note: This only applies to tape formats; there are no Media Format selections available for either Lattus or Storage Disks.

LTFS appears in the Configuration > Storage Manager Policies > Storage Manager tab (in the Steering column), and in the View page (in the Media Format column).

The LTFS media format also appears in the Reports > Media page (in the Media Format column).

Additional checks have been included in the StorNext Linux-based installation to ensure that some additional RPM packages required to support the LTFS media format are installed prior to installing StorNext. For LTFS requirements, see the StorNext Compatibility Guide, the StorNext Installation Guide, and the StorNext Upgrade Guide.