![]() It’s true that tape doesn’t offer the fast access speeds of hard disks or semiconductor memories. Storing that much data on compact discs would require more than 397 million of them, which if stacked would form a tower more than 476 kilometers high. And a single robotic tape library can contain up to 278 petabytes of data. Today, a modern tape cartridge can hold 15 terabytes. The first commercial digital-tape storage system, IBM’s Model 726, could store about 1.1 megabytes on one reel of tape. Like the hard disk and the transistor, magnetic tape has advanced enormously over the decades. Tape has been around for a long while, yes, but the technology hasn’t been frozen in time. There is even a cadre of people (including me, trained in materials science, engineering, or physics) whose job it is to keep improving tape storage. ![]() Indeed, much of the world’s data is still kept on tape, including data for basic science, such as particle physics and radio astronomy, human heritage and national archives, major motion pictures, banking, insurance, oil exploration, and more. So, a quick reality check: Tape has never gone away! Seriously? Tape? The very idea may evoke images of reels rotating fitfully next to a bulky mainframe in an old movie like Desk Set or Dr. And for such things, magnetic tape is the perfect solution. Fortunately, much of this information doesn’t need to be accessed instantly. ![]() At the same time, the capacity of modern hard drives, which are used to store most of this, is increasing at less than half that rate. Studies show that the amount of data being recorded is increasing at 30 to 40 percent per year. So companies and institutions of all stripes are holding onto more and more. And financial regulations now require organizations to keep records for much longer periods than they had to in the past. A unit of data written to or read from a tape is referred to as a block.It should come as no surprise that recent advances in big-data analytics and artificial intelligence have created strong incentives for enterprises to amass information about every measurable aspect of their businesses. The area on a partition between setmarks or filemarks is available for recording data. Tape devices that use filemarks support either short and long filemarks or normal filemarks, but not all three. A normal filemark does not contain an erase gap. A long filemark contains a long erase gap that enables an application to position the tape at the beginning of the filemark and to overwrite the filemark and the erase gap. A short filemark contains a short erase gap that cannot be overwritten unless the write operation is performed from the beginning of the partition or from an earlier long filemark. ![]() Support of both enables tape data to be formatted such that setmarks separate data from different disk volumes and filemarks separate data from individual files on a disk volume.Īnother recorded element that denotes locations on the tape is an erase gap, an area of erased tape or a pattern that the device does not recognize as a mark or as user data. Typically, tape devices support filemarks and setmarks. Filemarks and setmarks serve similar purposes, but setmarks provide faster positioning on high-capacity tape drives. Filemarks and setmarks are special recorded elements that do not contain user data they simply divide the partition into smaller areas to provide an address scheme. The area between a partition's beginning and ending points is typically divided into sections by filemarks or setmarks. The early-warning position notifies tape applications to transfer buffered data to the tape before reaching the end-of-partition marker. The early-warning marker is located immediately before the end-of-partition marker. The first position in a partition where you can record data is called the beginning-of-partition marker, and the last is called end-of-partition marker. Each partition has three predefined positions. A partition is a portion of the volume, containing its own beginning and ending points, that does not overlap with any other portion of the volume. The first position on the tape where data can be recorded is the called the beginning-of-medium marker, and the last position is called the end-of-medium marker.Įvery tape volume has one or more partitions. ![]() Short sections at the beginning and the end of the tape are reserved for attaching the tape to the hubs in the carrier. The entire length of tape in a volume is not available for recording data. A tape volume consists of a recording medium and its physical carrier. ![]()
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