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Drive suppliers hit capacity increase difficulties

PMR or HAMR for your platter?

Shingle writing

Barber reckons an interim capacity boost can come from 'shingle writing', which means overlapping tracks slightly, like shingle tiles on a roof, to cram more of them onto a platter surface. This will be done in conjunction with a larger sector size of 4K, but there will be a performance degradation because rewriting data means rewriting the whole track, not just a sector. Shingle writing is used "in external drives today … It's good for long large writes; not so good for transaction type environment with many short writes." You can't use the technique for enterprise drives because of the performance impact. The Seagate 3TB FreeAgent possibly uses the technique.

"This will extend areal densities towards 1Tbit/in2, maybe more." But then you are forced to go to a next-generation technology: "BPM is four to five years out, we think, because the lithographics are far from where they are needed to be today." The current supplier of such equipment to the HDD suppliers, ASML of the Netherlands, "have no machines capable of doing this year". Barber also mentioned that "Samsung has basically ordered every machine they can make this year".

"A couple of startups have sold one or two pieces of BPM equipment into labs for evaluation. It's a long way from being put into high-volume production." He is referring to Molecular Imprints and Obducat, and has doubts about their ability to survive for the next four to five years without orders from the HDD suppliers. "They have to spend a fortune on research and development. Customers won't buy in volume for at least five years." Obducat has recently undergone a reverse stock split - often a sign of financial tension.

The overall take-home from this is that we will see future capacity increases coming from an increased platter count in hard drives, both 3.5-inch and 2.5-inch, with a slowing down in areal density growth, and less frequent drive refreshes. External drives will diverge from desktop and enterprise drives because shingle writing will be used in the external drives but not the internal ones. We are going to see the life of PMR technology extended out to 2014 or 2015, and maybe HAMR will come in because it will be a less expensive next-generation technology to use than BPM. ®

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