ltfs

Linear Tape File System (LTFS)

Linear Tape File System (LTFS) is a filesystem to mount a LTFS formatted tape in a tape drive. Once LTFS mounts a LTFS formatted tape as filesystem, user can access to the tape via filesystem API.

Objective of this project is being the reference implementation of the LTFS format Specifications in SNIA.

At this time, the target of this project to meet is the LTFS format specifications 2.4. (https://www.snia.org/sites/default/files/technical_work/LTFS/LTFS_Format_2.4.0_TechPosition.pdf).

LTFS Format Specifications

LTFS Format Specification is specified data placement, shape of index and names of extended attributes for LTFS. This specification is defined in SNIA first and then it is forwarded to ISO as ISO/IEC 20919 from version 2.2.

The table below show status of the LTFS format Specification

How to use the LTFS (Quick start)

This section is for person who already have a machine the LTFS is installed.

Instruction how to use the LTFS is on Wiki. Please take a look!

Getting Started from GitHub project

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites

• Linux

  • automake 1.13.4 or later
  • autoconf 2.69 or later
  • libtool 2.4.2 or later
  • fuse 2.6.0 or later
  • uuid 1.36 or later (Linux)
  • libxml-2.0 2.6.16 or later
  • net-snmp 5.3 or later
  • icu4c 4.8 or later

• OSX (macOS)

  Following packages on homebrew

  • automake
  • autoconf
  • libtool
  • osxfuse (brew cask install osxfuse)
  • ossp-uuid
  • libxml2
  • icu4c
  • gnu-sed

• FreeBSD:

  • FreeBSD 10.2 or 11.0 or later (for sa(4) driver changes)
  • automake
  • autoconf
  • libtool
  • fusefs-libs
  • net-snmp
  • e2fsprogs-libuuid
  • libxml2
  • icu

• NetBSD:

  • NetBSD 7.0 or higher (for FUSE support)
  • automake
  • autoconf
  • libtool
  • libfuse
  • net-snmp
  • libuuid
  • libxml2
  • icu

Supported Tape Drives

Installing

LTFS Format Specification is specified data placement, shape of index and names of extended attributes for LTFS. This specification is defined in SNIA first and then it is forwarded to ISO as ISO/IEC 20919 from version 2.2.

The table below show status of the LTFS format Specification

How to use the LTFS (Quick start)

This section is for a person who already has a machine with the LTFS installed. Instructions on how to use the LTFS is also available on Wiki.

Step1: List tape drives

# ltfs -o device_list

The output is as follows. You have 3 drives in this example and you can use “Device Name” field, like /dev/sg43 in this case, as the argument of ltfs command to mount the tape drive.

50c4 LTFS14000I LTFS starting, LTFS version 2.4.0.0 (10022), log level 2.
50c4 LTFS14058I LTFS Format Specification version 2.4.0.
50c4 LTFS14104I Launched by "/home/piste/ltfsoss/bin/ltfs -o device_list".
50c4 LTFS14105I This binary is built for Linux (x86_64).
50c4 LTFS14106I GCC version is 4.8.5 20150623 (Red Hat 4.8.5-11).
50c4 LTFS17087I Kernel version: Linux version 3.10.0-514.10.2.el7.x86_64 ([email protected]) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-11) (GCC) ) #1 SMP Mon Feb 20 02:37:52 EST 2017 i386.
50c4 LTFS17089I Distribution: NAME="Red Hat Enterprise Linux Server".
50c4 LTFS17089I Distribution: Red Hat Enterprise Linux Server release 7.3 (Maipo).
50c4 LTFS17089I Distribution: Red Hat Enterprise Linux Server release 7.3 (Maipo).
50c4 LTFS17085I Plugin: Loading "sg" tape backend.
Tape Device list:.
Device Name = /dev/sg43, Vender ID = IBM    , Product ID = ULTRIUM-TD5    , Serial Number = 9A700L0077, Product Name = [ULTRIUM-TD5] .
Device Name = /dev/sg38, Vender ID = IBM    , Product ID = ULT3580-TD6    , Serial Number = 00013B0119, Product Name = [ULT3580-TD6] .
Device Name = /dev/sg37, Vender ID = IBM    , Product ID = ULT3580-TD7    , Serial Number = 00078D00C2, Product Name = [ULT3580-TD7] .

Step2: Format a tape

As described in the LTFS format specifications, LTFS uses the partition feature of the tape drive. This means you can’t use a tape just after you purchase a tape. You need format the tape before using it on LTFS.

To format a tape, you can use mkltfs command like

# mkltfs -d 9A700L0077

In this case, mkltfs tries to format a tape in the tape drive 9A700L0077. You can use the device name /dev/sg43 instead.

Step3: Mount a tape through a tape drive

After you prepared a formatted tape, you can mount it through a tape drive like

# ltfs -o devname=9A700L0077 /ltfs

In this command, the ltfs command will try to mount the tape in the tape drive 9A700L0077 to /ltfs directory. Of course, you can use a device name /dev/sg43 instead.

If the mount process is successfully done, you can access to the LTFS tape through /ltfs directory.

You must not touch any st devices while ltfs is mounting a tape.

Step4: Unmount the tape drive

You can use following command when you want to unmount the tape. The ltfs command try to write the current meta-data to the tape and close the tape cleanly.

# umount /ltfs

One thing you need to pay attention to here is, that the unmount command continues to work in the background after it returns. It just initiates a trigger to notify the the ltfs command of the unmount request. Actual unmount is completed when the ltfs command is finished.

The ltfs_ordered_copy utility

The ltfs_ordered_copy is a program to copy files from source to destination with LTFS order optimization.

It is written in python and it can work with both python2 and python3 (Python 2.7 or later is strongly recommended). You need to install the pyxattr module for both python2 and python3.

Building the LTFS from this GitHub project

These instructions will get a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites for build

Please refer this page.

Build and install on Linux

./autogen.sh
./configure
make
make install

./configure --help shows various options for build and install.

In some systems, you might need sudo ldconfig -v after make install to load the shared libraries correctly.

Parameter settings of the sg driver

LTFS uses the sg driver by default. You can improve reliability to change parameters of the sg driver below.

def_reserved_size=1048576

In RHEL7, you can put following file as /etc/modprobe.d/sg.conf.

options sg def_reserved_size=1048576

You can check current configuration of sg driver to see the file /proc/scsi/sg/debug like

$ cat /proc/scsi/sg/debug
max_active_device=44  def_reserved_size=32768
 >>> device=sg25 1:0:10:0   em=0 sg_tablesize=1024 excl=0 open_cnt=1
   FD(1): timeout=60000ms bufflen=524288 (res)sgat=16 low_dma=0
   cmd_q=1 f_packid=0 k_orphan=0 closed=0
     No requests active
 >>> device=sg26 1:0:10:1   em=0 sg_tablesize=1024 excl=0 open_cnt=1
   FD(1): timeout=60000ms bufflen=524288 (res)sgat=16 low_dma=0
   cmd_q=1 f_packid=0 k_orphan=0 closed=0
     No requests active

Performance improvement of the sg device

You can improve performance to change parameters of the sg driver below. But this option may cause I/O error reported as #144 in some HBAs.

allow_dio=1

In RHEL7, you can put following file as /etc/modprobe.d/sg.conf.

options sg allow_dio=1

At this time, we know following HBA’s works correctly.

• QLogic 8Gb FC HBAs

And following HBA’s doesn’t work correctly.

• ATTO ExpressSAS H680
• Emulex FC HBAs (Some drivers work but some drivers dont work, see this section)

Note for the lpfc driver (Emulex Fibre HBAs)

In the lpfc driver (for Emulex Fibre HBAs), the table size of the scatter-gather is 64 by default. This configuration may cause I/O errors intermittently when allow_dio=1 is set and scatter-gather table cannot be reserved. To avoid this error, you need to change the parameter lpfc_sg_seg_cnt to 256 or greater like below.

options lpfc lpfc_sg_seg_cnt=256

In some versions of the lpfc driver (for Emulex Fibre HBAs), the table size of the scatter-gather cannot be changed correctly. You can check the value is changed or not in sg_tablesize value in /proc/scsi/sg/debug. If you don’t have a correct value (256 or greater) in sg_tablesize, removing allow_dio=1 configuration of the sg driver is strongly recommended.

Note for buggy HBAs

LTFS doesn’t support the HBAs which doesn’t handle the transfer length of SCSI data by default. The reason is because the safety of the data but LTFS provides a option to relax this limitation.

You can use such kind of HBAs if you run the configure script with --enable-buggy-ifs option and build.

List of the HBA --enable-buggy-ifs is needed is below.

HBA list require --enable-buggy-ifs

IBM lin_tape driver support

You need to add --enable-lintape as an argument of ./configure script if you want to build the backend for lin_tape. You also need to add DEFAULT_TAPE=lin_tape if you set the lin_tape backend as default backend.

Buildable distributions

Dist	Arch	Status
RHEL 8	x86_64	OK - Not checked automatically
RHEL 8	ppc64le	OK - Not checked automatically
CentOS 8 (Rocky Linux)	x86_64
CentOS 8 (Rocky Linux)	ppc64le	OK - Not checked automatically
Fedora 28	x86_64
Ubuntu 16.04 LTS	x86_64
Ubuntu 16.04 LTS	ppc64le	OK - Not checked automatically
Ubuntu 18.04 LTS	x86_64
Ubuntu 18.04 LTS	ppc64le	OK - Not checked automatically
Ubuntu 20.04 LTS (Need icu-config)	x86_64
Debian 9	x86_64
Debian 10 (Need icu-config)	x86_64
ArchLinux 2018.08.01	x86_64	OK - Not checked automatically
ArchLinux 2018.12.31 (rolling)	x86_64	OK - Not checked automatically

Currently, automatic build checking is working on GitHub Actions and Travis CI.

For Ubuntu20.04 and Debian10, dummy icu-config is needed in the build machine. See Issue #153.

Build and install on OSX (macOS)

Recent Homedrew system setup

Before build on macOS, you need to configure the environment like below.

export ICU_PATH="/usr/local/opt/icu4c/bin"
export LIBXML2_PATH="/usr/local/opt/libxml2/bin"
export PKG_CONFIG_PATH="/usr/local/opt/icu4c/lib/pkgconfig:/usr/local/opt/libxml2/lib/pkgconfig"
export PATH="$PATH:$ICU_PATH:$LIBXML2_PATH"

Old Homedrew system setup

Before build on OSX (macOS), some include path adjustment is required.

brew link --force icu4c
brew link --force libxml2

Building LTFS

On OSX (macOS), snmp cannot be supported, you need to disable it on configure script. And may be, you need to specify LDFLAGS while running configure script to link some required frameworks, CoreFundation and IOKit.

./autogen.sh
LDFLAGS="-framework CoreFoundation -framework IOKit" ./configure --disable-snmp
make
make install

./configure --help shows various options for build and install.

Buildable systems

Build and install on FreeBSD

Note that on FreeBSD, the usual 3rd party man directory is /usr/local/man. Configure defaults to using /usr/local/share/man. So, override it on the command line to avoid having man pages put in the wrong place.

./autogen.sh
./configure --prefix=/usr/local --mandir=/usr/local/man
make
make install

Buildable versions

Build and install on NetBSD

./autogen.sh
./configure
make
make install

Buildable versions

Contributing

Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.

License

This project is licensed under the BSD License - see the LICENSE file for details