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Helium: Can it prevent the onset of Shingles?

Blimp gas is the write stuff

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Blocks and Files Filling disk drives with helium gas delays the time when shingled magnetic recording has to be adopted.

That's because helium gas-filled drives can cram more platters into a disk drive enclosure, thus increasing capacity without having to alter the data recording method. The current PMR (Perpendicular Magnetic Recording) process is nearing the end of its development as any further decrease in the size of the magnetised bits renders them unstable, and if you can't store data reliably then that's game over.

It is coming generally clear that PMR has to be followed by an energy-assisted recording method, such as Seagate's Heat-Assisted Magnetic Recording (HAMR), where localised heating of a bit is needed to alter its magnetic state, thus making it more stable and resistant to change at room temperature. But the development and implementation of HAMR-like technology could cost billions of dollars.

Enter Shingled Magnetic Recording (SMR) - we won't be vulgar and call it Herpes Zoster Recording although like that form of shingles it is undesirable - as an intermediate step. It uses PMR recording but partially overlaps tracks when writing, leaving narrower read tracks, and so crams more tracks onto a disk's surface thus increasing capacity. There is a major re-write problem though, as rewriting bits on one track alters the bits on the overlaid tracks. They have to be recovered first and then re-written, which slows rewriting down. SMR drives can't be used when fast writes are needed.

With helium-filled drives, Hitachi GST says, you use PMR recording but the resistance to spinning the disks in a helium environment is one tenth that of everyday air. This opens the way to having more platters in a standard drive enclosure, seven instead of four in a present day 4TB, 3.5-inch form factor drive, giving you 75 per cent more capacity and no diminution in write speed. Possibly the platters can be thinner, too.

Only WD subsidiary HGST has helium-filled drive technology, having cracked - it says - the notorious problem of helium leakage after many years of development. This implies it will take competitors Seagate and Toshiba some years to catch up while WD should inherit HGST's technology at no cost.

HGST can create a 7TB drive without using SMR or upgrading PMR technology, whereas Seagate and Toshiba will have to go to SMR, upgrade PMR technology into uncharted waters or go for a post-PMR recording technology. All three options involve spending money or entering the SMR world of slow writes.

Roof shingles

Roof shingles

Meanwhile HGST pumps gas into its drives, uses existing PMR and increases capacity by up to 75 per cent. I'd call that sitting pretty, and it can go to SMR if it needs to and increase capacity again, thus maintaining a capacity advantage over Seagate and Toshiba.

Shingled writing

Shingled magnetic recording

This assumes HGST (Helium Gas Storage Technology?) helium tech is solid and its drives won't leak and lose their helium-filled goodness. THere's also the point that increasing the platter and head count by up to three quarters could increase the number of points of failure in the drive and put reliability at risk. HGST needs to be on top of that issue.

Seagate and Toshiba engineers are possibly looking at drives with platters spinning in a helium atmosphere and hoping they could reverse-engineer the technology. HGST is confident that its hard-gained anti-leak smarts will stop them doing that and it has a multi-year advantage opening up. Of course, there will be no second source for helium-filled drives and that might slacken the wind in its sales, and even encourage a technology licensing scheme.

SMR is a stop-gap, an undesirable stop-gap. No-one wants to buy a new generation of disk drives that write data more slowly than the current drives. If helium gas drives delays shingled disks then customers will be all for it, because helium is the write stuff. ®

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