drive to write a second copy of any data that fails the verify without the help of the host system. Positioning times While specifications vary somewhat between different drives, a typical LTO-3 drive will have a maximum rewind time of about 80 seconds and an average access time (from beginning of tape) of about 50 seconds. Because of the serpentine writing, rewinding often takes less time than the maximum. If a tape is written to full capacity, there is no rewind time, since the last pass is a reverse pass leaving the head at the beginning of the tape (number of tracks ÷ tracks written per pass is always an even number). Durability LTO tape is designed for 15 to 30 years of archival storage. If tapes are archived for longer than 6 months they have to be stored at a temperature between 16 and 25 °C (61 to 77 °F) and between 20 – 50% RH. Both drives and media should be kept free from airborne dust or other contaminants from packing and storage materials, paper dust, cardboard particles, printer toner dust etc. Depending on the generation of LTO technology, a single LTO tape should be able to sustain approximately 200-364 full file passes. There is a large amount of lifespan variability in actual use. One full file pass is equal to writing enough data to fill an entire tape and takes between 44 and 208 end-to-end passes. Regularly writing only 50% capacity of the tape results in half as many end-to-end tape passes for each scheduled backup, and thereby doubles the tape lifespan. LTO uses an automatic verify-after-write technology to immediately check the data as it is being written, but some backup systems explicitly perform a completely separate tape reading operation to verify the tape was written correctly. This separate verify operation doubles the number of end-to-end passes for each scheduled backup, and reduces the tape life by half. Optional technology The original release of LTO technology defined an optional data compression feature. Subsequent generations of LTO have introduced new optional technology, including WORM, encryption, and partitioning features. Compression The original LTO specification describes a data compression method LTO-DC, also called Streaming Lossless Data Compression (SLDC). It is very similar to the algorithm ALDC which is a variation of LZS. LTO-1 through LTO-5 are advertised as achieving a "2:1" compression ratio, while LTO-6 and LTO-7, which apply a