Linear Tape Open (LTO) was developed in late the 1990’s for storing data on magnetic tape, using an open standard as an alternative to the many proprietary tape data cartridges. The LTO Consortium created through collaboration between Hewlett-Packard, IBM and Seagate, directs the development and manages all the licences for tape and drive manufacturers.
Ultrium is the name for the standard form-factor for LTO technology, the original version of which was released in 2000, capable of storing of uncompressed data. The LTO 6 data cartridges and drives released in 2012 are able to store 2.5TB of uncompressed data. Initially seen as a high end data storage solution, it is now affordable for small companies to use the older generation of tape cartridges and drives.
The LTO Ultrium was developed to be a replacement for the DLT data cartridge, also using half inch tape, and a similar size of cartridge, to allow easy modification of robotic libraries. Also like the DLT data cartridge, the recording is described as linear serpentine with the data stored in an outward spiral.
An important aspect of the LTO drives are that they are able to vary the speed at which the tape moves across the read/write heads, to alleviate one of the problems which can occur if the data is not being supplied at full bandwidth the drive is capable of writing data at. This cuts the number of times the tape drive is required to stop and reposition for the data write, which reduces the amount of tape ware, and reduces the unnecessary delays this would cause.
LTO in the Future
LTO Ultrium is now the bestselling tape data backup cartridge, having seen development of the DLT and AIT range of drives stopped. Further development of the DAT DDS range of drives and tape cartridge also appears to have come to a halt, leaving LTO as the only high capacity data cartridge still being developed.
The current roadmap for LTO Ultrium development details expected releases through to a 10th generation data cartridge capable of storing 48TB of uncompressed data on a single cartridge.
LTO Data Integrity and Recovery
In common with the DDS DAT recording format, the LTO Ultrium drive immediately reads the data written to tape, in order to verify that it was written correctly, which increases the reliability, but does not exclude the possibility of read errors when attempting to restore a backup. The most common issues requiring data recovery encountered with LTO Ultrium data cartridges, are operator or software related, from re-initialising the tape, overwriting a backup, or logical data corruption of the stored data.
The expected lifetime of an LTO Ultrium data cartridge, used for archival purposes is quoted as 15 to 30 years, which is dependent upon the conditions in which it is stored. Each cartridge is expected to last 5000 load and unload procedures, and approximately 260 full passes (writing or reading to the maximum capacity of the cartridge) before it is expected to fail. With the first tape cartridges released in 2000, any used to archive data may now start to be seen for data recovery from 2015 onwards.