The Magic Behind LTFS

hand with crystal ball

Disk Like Access with LTO Tape

Wouldn’t it be great if you could use a tape cartridge as if it were a disk drive?  To be able to look at the tape contents in a directory tree structure.  To drag and drop files to and from the tape!  Almost like holding the files in the palm of your hand!

LTFS and LTO technology make it possible to use tape storage more easily than ever before.  In this 3 part series you can learn all about the Linear Tape File System (LTFS): how it works, how to get started using it, customer use cases and benefits and offerings that are available from many providers that support this innovative tape file system!

In this BlogBytes let’s discover just what LTFS is and the magic that makes it so intriguing that it has become the standard for disk-like access on tape.

What is LTFS?

LTFS is a software driver that allows tape to be used in a manner like other storage drives.  The LTFS stand-alone drive software specification was adopted by the LTO Program in April 2010.  It is an open standard specification. The specification doc is posted at the website and can be downloaded there.  The LTFS specification has been adopted by SNIA for further development with an LTFS technical team that includes LTO consortium company engineers.

Until LTFS was created, a user needed proprietary backup software to utilize tape and then needed it to read the tape, because operating systems did not recognize tape. This dependency caused some ease-of-use issues. Now with LTFS, tape can be as easy to use as a USB memory stick or a removable hard disk drive. No traditional application software is needed.  The tape drive and its contents appear in the operating system’s graphical browser as a drive letter or folder.

LTO generation 5 and generation 6 tape drives have the capability to create two partitions on the tape cartridge. LTFS uses that capability to create a small partition to hold the tape index and metadata and store the content files in the second large partition. In addition, LTFS formatted cartridges can be interchanged between compatible drives and operating systems.  Support is available for versions of Mac OSX, Linux and Microsoft Windows.

How does LTFS do its Magic?

The Linear Tape File System format is a self-describing tape format and defines the organization of data and metadata on tape – files are stored in a hierarchical directory structure.

Again, it uses the dual partitioning capability introduced with LTO generation 5 and is available on LTO-6 drives too. Looking at the graphic in Fig-1, the first partition used by LTFS stores the index and metadata information.  The second partition is where all the content files are stored.

partition chart

Fig-1 LTFS Partitioning of Metadata & Content (BOT=Beginning of Tape; EOT=End of Tape)

When the tape is mounted in a tape drive, the index and information in the 1st partition is read and copied into the workstations memory. From that point on, the index is accessed and updated in the workstation memory for fast performance so the tape can keep positioned in the content portion of the tape to quickly access files.  As the tape is used, the index is updated in the workstation memory for fast performance, eliminating the need to go back to beginning of tape.

To protect the index, LTFS periodically copies the index from the workstations memory into the content partition. When the tape is done being used, the index is copied one more time at the last position used on tape, the tape is rewound and then the index is written into the first partition. Essentially, there are multiple copies of the index on tape for restoring in the unlikely event the first partition index is not usable or if a user wants to restore the tape to a previous version. For instance, you may want to restore it to the way the tape appeared last Monday by choosing an index from that date.

Access Content on Tape as if it were Disk!

Drag and drop

Fig-2 Drag and Drop Files to and from the Tape

Again, the accessing of files with LTFS on an LTO tape is similar to accessing with a disk, DVD, or USB thumb drive.  Use the OS browser, like Windows Explorer. When you bring up the browser you can see all of the storage devices on your workstation including the LTO tape.  You can drill down through sub-directories, open files from your applications on your workstation just like you are used to doing. You can drag and drop files to and from the tape (Fig-2).  It’s that easy.

In the next BlogBytes we will discover how to get started using LTFS and how others have implemented this amazing storage technology with LTO tape!

By the way, the LTO Program will be demonstrating LTFS live at booth #SL13010 in the south hall at the upcoming NAB show in Las Vegas this April 13-16. Come see the magic!