The Secret Life of Tape, 2011 Update


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In August 2006 I wrote an article exposing the fact that, like any device, tape has a life span. As all of you who read this column regularly know, I am a big proponent of tape and archival storage. I believe that given the hard error rate, the very low power usage and low cooling costs, and the lower cost per TB, tape is the best medium for long-term storage.

Like any medium, tape has a life span, and that life span is not just based on the interface becoming old and no longer supported. Some examples of the interface support issue include Fibre Channel 1 Gbit, Fibre Channel 2 Gbit and Fibre Channel 4 Gbit (likely soon), but that is not what I am talking about.

I am talking about the tape's life based the medium itself. Media wears out for a variety of reasons, including things like the stretching of the tape backing. There are many reasons, and the reasons are not the point of the column. The point is: What are the numbers? What are you going to do about it? What is missing from what vendors tell you, and want you to hear and not hear? Media technology wearing out is not limited to just tape media; it is also true of the disk drive. Again, I am not picking on tape! Try taking a consumer SATA drive, run it 7x24 doing head seeks and reading or writing, and do not try to tell me that flash does not have wear issues, either. Vendors address the flash by wear-leveling and adding extra cells. Anything that is electronic or mechanical will wear out. The real question is, what are the characteristics of this wear out, and what can you do to prevent it before the tape goes bad?

The Numbers

First of all, I want to thank the people at Imation for providing this information and updating the chart from 2006. The information Imation provided included many tapes that are no longer in use. I cut the chart down to what I consider modern tapes. What is clear from this chart is that if you read and write tapes very often, they will exceed what Imation says the tape is guaranteed to -- not that it will fail at that point, but when you exceed the expected usage. Note Imation's data is likely similar to other vendors, but no other vendors would provide the information publicly.

 ConfigurationLong-Length Durability *Example of Usage Life
Product NameUncompressed Capacity (native)Total Data Tracks Written On TapeData Tracks Written Each PassTotal EOL End-to-End PassesNumber of Passes to Write Full Capacity (native)Number of Full Capacity Writes/Reads (EOL)Years of Life Assuming 1 Full Capacity Write per Month **Years of Life Assuming 1 Full Capacity Write per Week **Total TB Processed Over Full Life Uncompressed
Imation T10000500 GB7683248002420017497.66
Imation T10000B1000 GB115232720036200174195.31
Imation LTO 1100 GB384896004820017419.53
Imation LTO 2200 GB5128160006425021548.83
Imation LTO 3400 GB704161600044364307142.05
Imation LTO 4800 GB896161120056200174156.25
Imation LTO 51500 GB1280161600080200174292.97

* Long-Length Durability test is typically performed at extreme environmental conditions, and is done without the benefit of cleaning between full capacity writes. Short-Length Durability test is a "shoe-shine" type test over 1 to 3 meters of tape.
** Estimates of life are obtained from long-length durability results using a full file pass as a basis.
No compression is used on any calculations. Compression is data dependant and can be between 1.5X and 2X (typically), up to 3X.
Limitations: This chart is only a guideline and may change dramatically based on the user's daily practices for the care and handling of the media, maintaining the proper use/storage environments, drive maintenance and a number of other factors.

These results beg the question: How long would it take to hit the tape wear-out levels if the drive was running at the full data rate for uncompressed for each of these tapes?

Product NameUncompressed Capacity (Native)Wear Time at Full Rate in HoursWear Time at Full Rate in Days
Imation T10000500 GB237.049.88
Imation T10000B1000 GB474.0719.75
Imation LTO 1100 GB406.3516.93
Imation LTO 2200 GB406.3516.93
Imation LTO 3400 GB517.1721.55
Imation LTO 4800 GB379.2615.80
Imation LTO 51500 GB609.5225.40

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