Magnetic Tape: The Challenge of Reaching Hard-Disk-Drive Data Densities on Flexible Media
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control, and error-correction coding overhead needed to compute an available capacity to the user. The product (bpi)(tpi) is the areal density in bits per square inch,and LW is the total recording surface area. Figure 1 shows the areal density progression for magnetic tape compared with HDDs. As of late 2005, the areal density of HDDs is 200 times that of linear tape, yet the capacity of a similar storage volume (a tape cartridge vs. a disk drive) is comparable at 300–500 Gbyte. This means that from a volumetric density perspective of the storage entity, the data storage density is about the same with 0.5 Tbyte tapes. The perception of tape as being low density has been solely based on areal density comparisons, but tape has been able to scale up the area of the recording surface significantly within a constant volume. In this article, we address specifically what is involved in scaling up the areal density of tapes. From the data in Figure 1, one can see that the linear density (bpi) of HDDs is only 2.7 times higher than today’s tapes, but the track density (tpi) is 75 times higher. If tape is to achieve the areal densities currently demonstrated by HDDs, the tpi is clearly the larger issue and is a direct result of the mechanical properties of the media.
Magnetic Tape: The Challenge of Reaching HardDisk-Drive Data Densities on Flexible Media Richard H. Dee Abstract By the end of 2006, the areal density of magnetic recording on tape will approach that seen in hard disk drives of the early to mid-1990s. These operating conditions are reviewed in relation to the operating conditions deemed necessary for the future of magnetic data storage on tape. What results is a clear set of tasks, encompassing both materials and systems architecture issues, to achieve very high-density data storage on magnetic tape, leading to 10 Tbyte tape cartridge capacities and higher. The key to achieving on tape the areal densities of tens to hundreds of Gbitin.2, common in hard disk drives (HDDs), lies primarily in the properties of the medium itself. As for volumetric density of the storage entity, HDDs and tape cartridges are roughly equivalent. The mechanical dimensional uncertainties that accompany the use of flexible, as opposed to rigid, media means that both the mechanical and magnetic properties of materials play a key role in the future of tape. The need for new architectures to overcome the track placement problem that results from increasing track density on flexible media are reviewed, as well as the “particles in a binder” concept that has served so well as the physical basis of tape media over the past 50 years.
Magnetic Tape: Now and in the Future
Keywords: magnetic properties, mechanical properties, memory.
Introduction Although magnetic tape has been around for a long time,1 the technology used to maintain the advantage of tapes as a lower-cost alternative for the increasingly large repositories of archived data is by no means old or outdated. In order to keep pace with the storage needs and the recent rapid lowering
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