HDDs Future is Perpendicular

Disk capacity will rise.

As storage capacity demands continue to increase, new serial technologies will gradually replace current parallel SCSI and ATA storage media during the next two years. Beyond these serial advances, hard-disk- drive vendors are working to develop even-more-advanced technologies to improve the physical data recording capacities of HDD magnetic media.

Many HDD manufacturers, including Hitachi Data Systems Inc., IBM and Seagate Technology LLC, are beginning to explore a new magnetic recording technology called perpendicular data recording. Based on the technologys potential capacity boosts, eWEEK Labs believes this is the shape of HDD storage to come. However, it probably wont emerge for several years.

Beyond perpendicular recording

Seagate is working on two additional technologies that will further increase areal density in recording media

  • Optically Assisted Magnetic Recording will use thermal energy (that is, lasers) to heat the media surface while data is being written, making it possible to write high-coercivity data to counter superparamagnetism
  • Self-Ordered Magnetic Arrays will convert grains of material in a single bit of data into unique bits of information that will orient in arrays that can be read and written with high thermal stability
In todays "longitudinal" HDD products, data bits are recorded on magnetic media using a recording method in which data bits are placed parallel to the media plane. Current longitudinal recording techniques can carry storage densities beyond 100 gigabits per square inch, but new recording methods will be necessary in the coming years to maintain the growth rate in HDD capacity, according to industry experts.

To achieve higher storage capacity, drive makers must increase the areal density of the magnetic media. Current methods involve making data bits smaller and placing them closer together, but there are several factors that can limit how small the data bits can be made.

As the data bits get smaller, the magnetic energies holding the bits in place also decrease, and thermal energies can cause demagnetiza- tion over time, leading to data loss. This phenomenon is called the superparamagnetic effect. To counter it, HDD manufacturers can increase the coercivity (the magnetic field required for the drive head to write the data on the magnetic media) of the disk. However, the amount of coercivity that can be applied is determined by the type of magnetic material used to make the head and the way data bits are written, and vendors are approaching the upper limits in this area.

Perpendicular recording places data bits perpendicular to the magnetic media surface. The data bits are formed in upward or downward magnetic orientation corresponding to the 1s and 0s of digital data. Perpendicular recording gives hard drives a much larger areal density in which to store data because it can achieve higher magnetic fields in the recording medium.

HDD vendors have been harnessing available technology to double their drive capacities every year, and advances in Serial ATA and SCSI drives will make large storage systems cheaper, faster and more efficient than before.

We therefore dont expect to see HDD systems that use perpendicular recording technology for several years, but this recording method will take future HDD systems to densities many times greater than the current longitudinal recording methods. Some experts estimate this new recording method can create areal density up to the terabit-per-square-inch range.

Further out on the horizon, Optically Assisted Magnetic Recording and Self-Ordered Magnetic Array methods could, in turn, eventually outrace perpendicular recording methods (see chart).

Imagine being able to store terabytes of data in your iPod or handheld devices—the possibilities are almost endless.

Technical Analyst Francis Chu can be contacted at francis_ chu@ziffdavis.com.