Back in 2000 the first generation of LTO (Linear Tape Open) was introduced. LTO-6 is now well entrenched offering capacities of 6.25TB at a compression of 2.5:1, with the next generations of LTO-7 expected to offer 16TB with a transfer rate of 788Mb/sec. Read and write backwards compatibility for two generations and read compatibility across all formats is integral to LTO. However IBM and Fujitsu are taking this a stage further with densities of 85.9billion bits per square inch which could give us 154TB tapes!
LTO remains one of the best cost effective options for long term storage and archiving. Disk arrays are expensive and hard drives are not built for the long term archival of content, due to the inherent architecture which makes them prone to failure from inactivity. LTO on the other hand is built for storing files rather than analogue data and the LTFS file system is an open and more efficient way to access tape. It is the first standard that defines a file system for tape and makes a tape look like a hard drive.
Even so, why is tape still so popular? Unlike a hard disk drive with moving parts and electronics, an LTO is essentially still a spool of tape with no moving parts. Heads, motors and actuators are located in the LTO tape drive, which makes the tapes much more resilient to failure.
Tape is designed to sit inactive for 30 years and transfer speeds are nearly two times that of a hard drive. Also LTO employs verify after write technology. Quite simply a read head follows the write head to verify data as correct. This provides automatic check-summing which makes archiving so much faster – almost four times faster than archiving to a removable hard drive. The latest generation has been resurrected with improved tape media specifications, stronger magnetic properties and more read/write heads to achieve a higher track density. For all these reasons, LTO has survived where many other tape formats have died as technology passes them by. One drawback is that a hard drive allows the user to access memory randomly. Tape is still unable to offer this level of functionality and is why it is not an alternative to hard drives for day to day use. However as an archiving tool, LTO is likely to remain the preferred option for many decades to come.