Pushing The Boundaries of Data Storage in the Information Age
Keeping our networked, digital world up and running depends on storing, accessing and managing tons of data that is multiplying and growing dramatically every day. Where does it all come from? Where does it all go? And what will make sure I can continue enjoying my digital lifestyle? The answer is storage technology, like that found in disc drives. The ability for storage technology to continue its rapid pace of advancement is critical for people around the globe to have the world's information at their fingertips.
The growth of storage in our Information Age has exploded largely because of the ability to continue to deliver it inexpensively. But current technology presents limits to how much information can be stored on a disc drive. This means that eventually people may no longer be able to get twice the capacity each year for the same price as the previous year. With storage demands rising, it is critical that technologists develop the technologies that will continue to allow affordable storage for everyone.
The ability to store a given amount of information on a disc drive is driven largely by a drive's areal density. Areal density refers to both the size and how closely spaced the information bits are on a disc drive. By increasing the areal density on discs through the process of making the information bits smaller and more closely spaced, more data can be put onto the discs, meaning fewer discs and parts can be used inside a disc drive. With current storage technologies, there is an areal density limitation and technologists are working on needed storage breakthroughs for the next millennium. This is critical when considering how much storage people have continued to demand and use.
During the past five years especially, the demand for magnetic storage has grown at a tremendous rate. Key areas such as the Internet as well as networks and databases that create and use information for business have fueled this growth. With the increased need for storage, technologists working in the field continue addressing the challenge of increasing disc drive capacity while also making them faster. The bottom line is that if new breakthrough technologies aren't successfully implemented that can keep up with storage demands while overcoming areal density limitations; an inherent slowdown of information can occur that could inhibit businesses and people throughout the world. Additionally, issues such as much greater storage costs as well as capacity limitations are a part of this scenario. Given the demand and need for electronic information in our digital world, it is critical that this not happen.
Facts About Storage Use
Several factors contribute to this demand for storage. Internet traffic is approximately doubling each year, according to the recent 2001 report by Coffman and Odlyzko entitled, "Is there a Moore's Law for data traffic?" And ETForecasts discovered that home Internet use itself has quadrupled since 1995, going from 9 percent to 41.5 percent of all homes in less than 5 years. It was also Odlyzko in an earlier 2000 report, "Content is not King" who wrote that communication such as e-mail was "the killer app" that required an enormous amount of storage capacity, not web content. In fact, the UC Berkley team also affirmed this by reporting that approximately 610 billion e-mails are sent per year.
When moving outside of the Internet arena, storage used for business networks and databases is also expected to grow rapidly. In fact, International Data Corporation estimated that implementations such as Network Attached Storage (NAS) and Storage Area Networks will both grow to a combined revenue of $18.6 billion by 2003. Additionally, storage services worldwide are expected to top $40 billion.
Pushing the Technology Boundaries - The Technical Details
Disc drives at their most basic level work on the same mechanical principles as media such as compact discs or even records, however, magnetic disc drives can write and read information much more quickly than compact discs (or records for that matter!). The specific data is placed on a rotating platter and information is then read or written via a head that moves across the platter as it spins. Records do this in an analog fashion where the disc's grooves pick up various vibrations that then translate to audio signals, and compact discs use a laser to pick up and write information optically.
In a magnetic disc drive, however, digital information (expressed as combinations of "0's" and "1's") is written on tiny magnetic bits (which themselves are made up of many even smaller grains). When a bit is written, a magnetic field produced by the disc drive's head orients the bit's magnetization in a particular direction, corresponding to either a 0 or 1. The magnetism in the head in essence "flips" the magnetization in the bit between two stable orientations. In currently produced hard disc drives, longitudinal recording is used. In longitudinal recording, the magnetization in the bits is flipped between lying parallel and anti-parallel to the direction in which the head is moving relative to the disc.
Increasing areal densities within disc drives is no small task. For the past couple of years, technologists have been increasing areal densities in longitudinal recording at a rate in excess of 100% per year. But it is becoming more challenging to increase areal densities, and this rate is expected to eventually slow until new magnetic recording methods are developed.
To continue pushing areal densities in longitudinal recording and increase overall storage capacity, the data bits must be made smaller and put closer together. However, there are limits to how small the bits may be made. If the bit becomes too small, the magnetic energy holding the bit in place may become so small that thermal energy may cause it to demagnetize over time. This phenomenon is known as superparamagnetism. To avoid superparamagnetic effects, disc media manufacturers have been increasing the coercivity (the "field" required to write a bit) of the disc. However, the fields that can be applied are limited by the magnetic materials from which the head is made, and these limits are being approached.
According to Dr. Mark Kryder, senior vice president at Seagate Research, longitudinal recording still has time left before reaching the superparamagnetic limit. "We expect today's longitudinal recording methods to take us beyond 100 gigabits per square inch in density. A great challenge however is maintaining a strong signal-to-noise ratio for the bits recorded on the media. When the bit size is reduced, the signal-to-noise ratio is decreased, making the bits more difficult to detect, as well as more difficult to keep stable."
Perpendicular recording is widely seen as the next method of recording that will be adopted to help push areal densities further. Dr. Kryder estimates that the switch to perpendicular recording will occur sometime between 100 and 200 gigabits per square inch areal density. In perpendicular recording, the magnetization of the disc, instead of lying in the disc's plane as it does in longitudinal recording, stands on end perpendicular to the plane of the disc. The bits are then represented as regions of upward or downward directed magnetization (corresponding to the 1's and 0's of the digital data).
Perpendicular recording enables one to record bits at a higher density than longitudinal recording, because it can produce higher magnetic fields in the recording medium. In perpendicular recording the media can be deposited on a soft magnetic underlayer that effectively produces an image of the recording head and approximately doubles the recording field.
Even though perpendicular recording will take magnetic recording technology much further than the current longitudinal methods, superparamagnetic effects still exist at some point, though it is difficult to predict exactly when this will occur.
"At this time, we estimate that perpendicular recording methods may take us all the way to one terabit per square inch," Dr. Kryder continued. "When that level is reached, a single 3.5 inch disc will store over one terabyte of information."
While that amount of storage is a significant advance beyond that of storage capacity available in a single drive today, when put into perspective with the best estimates and forecasts of our current and future storage requirements, the need for technologists to continue to forge ahead beyond that figure is clear. The UC Berkeley study reported that the world produces between 1 and 2 exabytes (one exabyte is the equivalent of one billion gigabytes) of information each year in total, comprising all magnetic, paper, film, and optical data. In addition to that sum, it is conceivable that eventually much of the older media such as those produced on film and paper may also make its way to magnetic data translation, increasing the overall total figure further.
Further Into the Future
Beyond longitudinal and perpendicular recording, technologists are already beginning to explore other possible methods of recording data. Still many years away, optically-assisted (also known as thermally-assisted) magnetic recording, or a type of patterned or self-ordered magnetic array are viewed as possible candidates for storing the world's information.
Optically-assisted recording involves producing a hot spot (commonly with a laser) on the media, while data is simultaneously written magnetically. The net effect is that when the media is heated, the coercivity or field required to write on the media is reduced, making it possible to write high-coercivity media (which as explained above have higher stability against superparagmagnetism), in spite of the limited fields that can be produced by recording heads.
Technologists such as Seagate Research's Dr. Dieter Weller are also working on patterned media, or what is also being called self-ordered magnetic arrays (SOMA). "A typical bit of information is made up of about 100 grains of material. We are working to convert each grain to a unique bit of information. As a result, a large gain in bit density would be achieved," said Dr.Weller.
Dr. Weller added that Seagate Research is working on ways to make the grains "order" in a regular array so that the bits can be read and written and so that good thermal stability can be achieved. Weller believes that iron platinum (FePt) is the best material to use along with a careful balance of other chemicals.
Probe storage may be one of the more unusual methods of recording proposed since it doesn't involve the use of discs at all. Rather, probe storage technology could be implemented in something the size of a typical semiconductor chip. It works like a scanning microscope, except there is an array of these microscopes or probes that read and write the data. Each probe addresses an array of bits of information, and the probes write and read in parallel. Several media candidates are under consideration, including magnetic media, and, unlike typical silicon chips, they won't lose memory once power is turned off. It is estimated that about 10 gigabytes of information will be able to be stored on a centimeter-sized chip.
While probe storage offers interesting possibilities, Dr. Kryder doesn't view it as a replacement for disc drives. Rather, he envisions probe storage chips working in a large number of consumer electronic devices that require a solid state, low-power storage device with moderate capacity. He even envisions them being put into disc drives to act as a memory buffer to allow faster access to information than the drive alone can provide.
The Information Age Continues
With computers firmly entrenched in our world, the need for more storage has never been greater. While it is difficult to truly estimate how much storage we will need and use in the future, there is no debate that the figure is astronomical. At no other point in the history of mankind has there been such a thirst for so much information. As a result, in this Information Age achieving the goal of allowing the average person access to all recorded information ever produced, is a significant, yet important one. It is information after all, that will ultimately help move us into newer and greater eras of enlightenment and discovery.
POWER-THRIFTY HITACHI HARD DRIVE MAKES FOR COOL LAPTOPS,
About Hitachi Global Storage Technologies
Over the last four years, a new generation of consumer devices has radically changed the way people accumulate, enjoy and store entertainment. At the heart of the latest consumer electronic devices is what Hitachi is affectionately calling the new "Bling" - hard disk drives. These incredible shrinking drives have been instrumental in driving the digital revolution and a series of announcements from Hitachi today will drive future developments:
Hitachi unveils terabyte DVD recorder