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Tale of the Tape: Musings on IBM’s 35TB Tape Announcement

A recent tweet by Chris Mellor from The Register caught my eye. He highlighted IBM’s recent development of a 35TB tape. Here are four articles on the topic:


FUJIFILM Announcement

The Register Article

A blog post by Robin Harris at ZDnet

My thoughts

It is interesting to see IBM/Fuji driving tape development. With this announcement they have increased native tape capacity over 21x from LTO-5, the newest LTO offering. The dramatic density improvement will drive a continued decrease specification-based $/GB. However it also raises some new questions:


If performance is unchanged from LTO-5 and you could stream the drive to maximum specifications and achieve 2:1 compression, it would take about 35 hours of continuous backup to fill the cartridge. Wow, that is a long backup window! Chris Mellor in his Register article linked above suggests some alternative approaches to performance including striping multiple tape drives and adding more write heads to drives. Regardless of the method used, it appears that these new tapes will have to be streamed much faster than any previous tape technology. This will create infrastructure challenges; the IT team must ensure that they have enough bandwidth through the backup process to stream the drive. The concept of shoe-shining becomes particularly painful here since the minimum data transfer rate will also increase.


This new high density tape can create $/GB economic challenges both for DR and in the model Chris suggests of striping across drives. The acquisition cost for these tapes will be substantial. If you assume the same $/GB as LTO-4, each of these new tapes will cost about $1,400! Clearly the real world price will be much less, but the cost will increase. The challenge is that the best $/GB is achieved when the tape is filled and compressed. Thus, the best ROI is achieved when you have stored 70 TB of data on the tape (assuming 2:1 compression). If you are using tape for DR, it becomes even more challenging because you want to fill your tapes and your backup jobs will not typically fit in consistent 70TB increments. If you do not manage this effectively you will end up sending hundreds of partially filled tapes offsite which will destroy the ROI.

The situation above gets worse if you look at Chris’s model of striping data across multiple drives. Now your maximum capacity increases linearly with the number of drives. If you assume four drives then your ROI is only maximized when you store 280 TB of data. These numbers get maddeningly large very fast.

Risk of data loss

Now imagine that you have resolved the performance and $/GB issues. You are comfortably filling each tape to its max of 70TB. The challenge now becomes one of data protection. With so much data on one tape, what happens if the tape is lost? What happens if it is unreadable for whatever reason? You are now placing a much larger bet on the reliability and consistency of these tapes than ever before. Are you really comfortable storing so much data on a single piece of relatively unreliable medium? Of course, you place the same bet on tape today but the lower capacity means that an individual tape failure will have a reduced impact.

Clearly the development and launch of massively dense tape can in the right circumstances provide business value. However, I believe that customers must evaluate these technologies in the context of their business SLAs and budgetary requirements and that the new technology will be hard to justify in many instances. Of course, the final specifications have not been announced and so it is possible that the actual product released will be different from the one announced today. I am curious to see the final product and how/if they address these concerns.

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