bcmt349 Homework - PMR and the Hitachi TB Hard Drive

I really am not big on the latest and greatest hard dives that are available for the average person to buy, but what really grabbed my attention was the use of a different technology that has allowed hard drive manufacturers to increase the capacity of the available hard drives while drastically cutting back on the data loss associated with older high capacity drives. This technology is called Perpendicular Magnetic Recording (PMR). Basically, the alignment of the bits of information located on the disk surface is changed to make the bonds between them stronger and more reliable while makin use of a now smaller footprint to add storage capacity.

In class we discussed how older hard drives are affected by the tremendous heat generated by the rotation of the disk of the hard drive. As the heat increases the material of the disk can distort, causing the reader head to impact or rub the disk resulting in data loss. On these disks the bits are layed horizontally, like tiles laid out on the floor. PMR essentially stands the bits on their ends and brings them together to make additional space on the disk for storage. The additional benefit is that the bits are now connected using the larger part of their surface to each other, making their bonds stronger and reducing the effects of additional heat and distortion that can chane the magnetic properties of the bits and make them more suseptible to loss. Think of two rectangular bar magnets. If you connect them end to end you can detach them fairly easily. Now connect them at their largest surfaces. Much more difficult to break apart!

For this exercise I focussed on Hitachi's Deskstar 7K1000 terabyte hard drive. Now it is not very new to the industry, but it incorporates the PMR I discussed above and it integrates a thermal sensor to deal with the heat generated by the 7200 RPM operating speed of the disk. The thermal sensor monitors the heat being generated during operations and requests additonal air flow from the cooling fans through the CPU to maintain temperatures within the accepted operating range. Hitachi also has a controller installed to maintain the reading heights of the reading arm through various operations to further control friction and resulting operating temperatures.

These technologies are still in their early stages, but already Hitachi plans on releasing a 2 TB hard drive by late 2009 utilizing these same advances.


http://www.hitachigst.com/hdd/research/recording_head/pr/perpendicularAnimation.html
http://www.pcworld.com/article/131417/hitachi_deskstar_7k1000.html

http://www.hitachigst.com/portal/binary/com.epicentric.contentmanagement.servlet.ContentDeliveryServlet/hgst/products/images/get_perpendicular_small.jpg

http://www.hitachigst.com/portal/site/en/menuitem.8027a91c954924ae4bda9f30eac4f0a0/

http://www.hitachigst.com/tech/techlib.nsf/techdocs/67A68C59B27368FC862572570080FC70/$file/Deskstar7K1000_010307_final.pdf