News

posted on 11 July 2008 11:36

Hitachi GST is claiming its developing CPP-GMR read/write head technology can lead to 5TB hard drives by 2010.

HGST has just announced a 1TB 3-platter 3.5-inch SATA disk drive with 375GB per platter. Seagate has just announced a 1.5TB drive with 4 platters and thus the same areal density. If we assume that the 5TB HGST drive will be a 4-platter product then it will have 1.25TB per platter, a 3.3 times increase on the current areal density. A 3-platter 5TB drive would require a 4.2 times improvement.

Commensurate increases on 2.5-inch drives, currently reaching 500GB will mean 1.5TB drives in 2010.

CPP-GMR stands for Current-Perpendicular-to-Plane Giant MagnetoResistance and involves a change from the current TMR (Tunnel MagnetoResistive) heads. As hard disk drive (HDD) track widths shrink the read/write head needs to shrink too. However reducing a TMR head in size leads to greater electrical resistance, signal noise and performance loss.

A TMR head has an insulating layer between two magnetic layers with electrons tunnelling through the layers as the head reads or writes data on the drive. Electrical current flows parallel to the insulating layer. This works well at the current 200Gbit/sq in areal density, with tracks about 70 nanometres apart, but apparently becomes unfeasible at areal densities approaching 500Gbit/sq in.

With a CPP-GMR head there are two magnetic layers with a conductor, probably copper, between them and the electrical current running at a perpendicular angle to this. Apparently there is less electrical resistance with this design and the head can be reduced in size. That means they can read and write signals with tracks 50nm apart or even closer. HGST expects product with 50nm track separation in 2009 and 30nm separation in 2010.

HGST expects to ship the first CPP-GMR head-equipped products either in 2009 or 2010.

However, the HGST claim only identifies one side of the coin as there has to be a way to lay down small enough tracks on the disk platters. HGST has taken delivery of a BPM machine. Fujitsu and other HDD manufacturers are also working on BPM (Bit-Patterned Media) for this featuring nanoholes.

We might expect HGST to announce a 2.5TB 4-platter drive in 2009 and then their 5TB 4-platter model in 2010, if the company keeps to its schedule.

Seagate has very recently announced a $228 million investment in its Londonderry, N. Ireland, read/write head plant.

RAID rebuild times on 5TB drives could be so long as to make current schemes like RAID 5 impractical.

^{[Paul Roberts, news editor.]}