How Google taped up its email outage wounds
Is there still a role for the reels ...
HP puts in its two cents
As one of the main tape automation format developers with DAT in its locker, plus LTO Consortium membership – and its position as a strong cloud evangelist – HP's views on tape in the cloud should be interesting.
Here is its starting position:
Cloud service providers should be aware that LTO tape technology is expanding its role from a pure backup solution to that of a premier long-term storage technology and archive.
The company echos the Spectra view about the respective roles of tape and disk in backup and archiving. Asked about the relative costs of tape and disk, HP said:
At approximately 6 cents per Gbyte (native) for LTO-5 tape media, LTO Tape offers one of the lowest costs per Gbyte for long-term storage, particularly when factoring in energy costs. Tape storage is cool – literally – and has been shown to decrease storage power requirements by 99 per cent when compared with disk-based storage. Tape helps meet the goal of many data centres that inactive data should not consume energy.
Data archived on tape does not require the data centre floor space, power or cooling that's required for data stored on disk ... The Clipper Group Inc studied the total cost of ownership (TCO) of using disk or tape to archive large binary files ... [and] concluded that:
The Clipper Group said: "In every dimension, the TCO of the tape solution was found to be less expensive than the TCO of the disk solution for long-term data retention, especially for energy consumption, where disk consumes 238 times as much energy as tape under assumptions that lean toward favouring disk. For most uses, we believe that the vast majority of archived data should reside on tape."
- Disk is more than 15 times more expensive than tape for archival.
- Disk uses 238 times more energy - costing more than the total cost of the tape solution.
HP provided an example that illustrates how tape restore speed can be faster than disk restore speed:
When writing/recovering large quantities of archive data, tape's streaming rates (280MB/sec in the case of LTO-5) give tape a performance advantage over disk (SATA 3Gbit/s can support sustained throughput rates of 250-260MB/sec).
Gabriel Chaher, senior director of international product and field marketing for Quantum, agreed with HP and Spectra on tape's cloudy role, and notes that, generally, "tape is part of a tiered storage solution."
Chaher addresses deduplication as an issue, citing a Clipper Group report, and saying:
[The] average disk storage is about 15 times the cost of average tape storage. The assumptions in the report do not account for a difference resulting from deduplication (for archive) because of the following reasons:1 The nature (less dedupable) of target archival data.
2 The fact that any deduplicating is getting done upstream of the final archiving tier.
3 There would be a need to preserve the deduplication engine to be able to reconstruct the data, which may be stored for very long periods of time.
If it were to become practical to store deduplicated data on tape – say via a tape library with an integrated deduplication front end server – then we would expect tape's capacity to substantially increase, further improving its costs relative to disk, but we would lose the portability associated with standard tape formats, unless, and this is a huge "unless", the reduplication was done in a standard way.
Perhaps the three members of the LTO Consortium: HP, IBM and Quantum could devise a way for this to happen?
On the marketing front, Chaher has this idea:
Maybe tape storage is a lower cost alternative that cloud providers could pass on to their customers. (Example: Pay $100 / TB / month for "fast access storage", but pay $75 / TB / month for "slower access storage").
Quantum says it has "several online backup provider customers using our tape products but unfortunately we're not able to disclose which ones just yet."
Where does this leave us?
Tape is the final rescue for cloud disk storage screw-ups, like that of Gmail. There can realistically be no argument about this; it worked for Google when there was no alternative.
The financial arguments in favour of tape versus disk for long-term storage seem strong and sustainable. Tape capacities, like disk capacities, are increasing and so tape's relative advantage should be sustainable.
The use of tape reels in the cloud is already reality, and one would think that the Google Gmail incident will ensure its continued and growing take-up. The front-end backup storage tier will be disk for fast access, but the archive tier – where data is infrequently accessed – should be tape: for cost, off-site protection and energy use reasons. ®
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