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Archive for January 2011

Is Cloud based Tape Backup a great new business?

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I am certainly not an expert in tape storage, but the question is interesting. It has been said that “Disk is the new Tape” at Chirp 2010 in the presentation Scaling Twitter, but is it really? Could it make sense for somebody to buy a massive tape library, bolt on a REST interface and charge for tape on a pay as you backup model?

To start, let’s assume that there’s some clever way to work out putting data on tape for each specific user so that tens of separate tapes don’t need to mounted by the robot to retrieve data, all the while serializing the writing of data to tape. There is surely enough cleverness out there with the help of some disk caching to do this intelligently. Alternatively it could be an archival feature of current cloud offerings. Now what does tape cost in big volumes really? The math of this one is tricky because the medium is not what costs the most money. Some San Diego Supercomputer Center researchers gave the math a shot and their findings seem well thought through. The article states a price of $500/year/TB for one copy.

The same article also states that the price for storage at Amazon S3 is $1850 TB/year + $205 to initially store the data. Clearly AWS S3 provides a higher quality of storage with more than 1 copy and much more readily available access. Wow, the cost difference is around a factor of 4! Hmm, ,so maybe it would be possible to create the Acme Cloud Tape Backup Service and make a killing! After all Cloud Storage is sometimes referred to as WORN Storage anyway (write once – read never) A mammoth installation should be able to provide tape at more economical prices than this study would indicate, bringing price still lower; now this starts to really look interesting!

Then again, there are some counter arguments:

  • For a near-line storage offering to be interesting, it would need to be as reliable and much less expensive than disk based storage. One tape copy will never do, so we better take 2 copies cutting our profits in 1/2 and raising prices to $1000/TB/year
  • Even though folks use cloud storage for backup, it’s way more responsive than it needs to be for backup. After all, it’s fast enough to serve up web pages with; now just try that with tape! We could imagine a website with a new URI, say tape:// with a nice blinking Javascript banner saying Please wait while the Robot loads your request…

  • We must also admit that the cost of using disks can realistically be significantly reduced by using different redundancy models such as dispersed storage like Cleversafe and Amplidata propose. It is surely possible to reach the $1000/year number if disk storage is allowed latencies and I/O performance similar to tape values.

  • Tape has power consumption arguments in its favor, but it would be fairly simple to power down full hard drives and achieve similar results.

  • The level of investment in hard drive technologies speaks in their favor over time, especially when much of the cost in tape is associated with physical handling of tapes by robots and humans; costs that are not subject to Moore’s laws or its derivatives.

  • Another advantage of hard disks is their ability to tell us when they are failing and need replacement. Tapes on the other hand must simply be replaced on a regular schedule, because, especially with a single copy, when read errors occur due to tape degradation it is simply too late.

The question is interesting though. We have to admit, tape is still cheaper than disk, and it doesn’t consume power remembering what you asked it to remember. So yeah, I think there just might be a market, but whoever does it better be very good at what they do.

One last thought:
You have to admit Exabyte was a very cool and forward looking name for a tape drive company!
On the other hand their site is Temporarily Unavailable today.


Written by Giorgio Regni

January 14, 2011 at 5:58 pm

Posted in Cloud Storage, Storage