Cold storage: The next frontier for IT data management

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cold storage

Cold storage made a big splash in the IT world last year when Facebook announced that it was going to store 7,000TB of users’ pictures in a cold system, without shedding more light on how exactly it intended to proceed. Adetailed document published by Mike Yan, a hardware engineer at Facebook, on

the Open Compute website in

January, should give you a fairly precise idea of what Facebook is working on, but the concept behind cold storage is actually deceptively simple. A virtual container thatstores data that is almost never read again, but must be kept either for legal requirements or as a backup of third copies of data for disaster recovery scenarios.

Berger was also keen to highlight two different types of cold storage, one called “cooling/warm online storage” with latency of around 100ms, while proper cold storage has minute/hour latency. Both have different media access profiles and different audiences. Moreover, a number of significant announcements and improvements over the last year or so are on the verge of making cold storage a market reality.

The first of these is

helium-filled hard disk drives

. Helium allows contemporary HDDs to dramatically improve their current storage capacity without any major retooling.Other than the lack of “breather holes," this new generation of hard disk drives won’t be designed differently compared to existing HDDs. The only other major difference will be the number of platters that can be crammed in the hard disk chassis. Berger confirmed to that the first commercially available helium-filled HDD will be available in November 2013 with seven platters and a 6TB capacity.

Second generation helium-filled hard disk drive models will have an even higher areal density. HGST introduced 2.5in platters with a 636GB/SI back in September 2011, a roughly 12 per cent storage capacity improvement compared to the previous generation. We suspect that further minor bumps in areal density are likely, bringing it closer to around 700GB/SI, and that these will be the platters likely to feature in next-generation helium HDDs.

The second important improvement is SMR (shingled magnetic recording). While adopting SMR will result in a loss in performance due to its intrinsic nature - write performance is likely to be a magnitude lower compared to current mainstream HDDs - that will be tempered by an increase in areal data density and a bump in platter count, withSMR potentially adding anywhere between 10 per cent and 25 per cent to the areal density.The first round of products based on this technology are likely to hit the market late next year, specifically targeting the rapidly evolving hyperscale/cold storage arena.Interestingly enough, Seagate recently announced that it had notched one million SMR drives and expected a 20TB hard disk drive to become a common SKU by the end of the decade.

Last but not least is the ever decreasing cost of compute power - both in terms of actual cost and power cost. It is expected that hard disk drive manufacturers will embrace on-the-fly hardware compression just like tape outfits to beef up their numbers and level the playing field.It is worth nothing that a new alliance, the SPA (

Storage Products Association

), was formed in August 2013 by the four major remaining hard drive manufacturers (bar Samsung). It aims to “promote the use and understanding of rotating magnetic media hard drive” in a bid to fend off growing competition from SSD and eventually kill off tape once and for all.

To achieve the death of tape, the cost of HDD storage must be much lower, allowing spinning hard drives to compete price-wise with tape and essentially make DDT (disk-to-disk-to-tape) obsolete. That could be achieved by 2018 and may well involve reviving the 5.25in format, given that many of the issues associated with cramming larger platters are now being tackled.

hierarchy of storage devices fullwidth

A 2.5TB LTO-6 tape cartridge, a format that was released in December 2012,can now be bought for under £65, which at 2.6p per GB is slightly more than the cheapest per GB cost for hard drives (although the drive itself costs north of £1,400). LTO-7 and LTO-8 are already in the pipeline with native capacities bumped to 6.4TB and 12.8TB - these are likely to be launched in 2014/2015 and 2017/2018, respectively. Assuming that tape media prices are constant, it is likely that the price per TB for tape will hover around £5.50 in 2018, by which time 20TB hard disk drives should be fairly common in IT and the enterprise.

Berger has even more aggressive expectations. He expects the price of a "tape" TB to be around £5 by 2016 and that of cold storage around £10 in the same year, mentioning that the price per TB for cold storage would be around half that of enterprise models initially.

It is worth noting that the latest improvements announced in the field of magnetic data recording (including HAMR,bit-patterned mediaandnano-imprinting) aims at boosting storage density rather than lowering access time or increasing throughput, a clue that SSD has perhaps durably and definitively established itself as the performance king.

Desire Athow isa technology journalist with nearly 15 years experience writing for UK publications, including and The Inquirer.