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ed new reel to reel products replacing them with cartridge based products beginning with its 1984 introduction of the cartridge based 3480 family citation needed dec format edit dual drive dectape unit linctape and its derivative dectape were variations on this round tape they were essentially a personal storage medium 15 used tape that was 0 75 inches 19 mm wide and featured a fixed formatting track which unlike standard tape made it feasible to read and rewrite blocks repeatedly in place linctapes and dectapes had similar capacity and data transfer rate to the diskettes that displaced them but their access times were on the order of thirty seconds to a minute citation needed cartridges and cassettes edit this section needs more citations please help improve this section by adding citations to reliable sources unsourced material may be challenged and removed september 2025 learn how and when to remove this message an ibm 3590 data cartridge can hold up to 10 gib uncompressed in the context of magnetic tape the term cassette or cartridge means a length of magnetic tape in a plastic enclosure with one or two reels for storing the tape the type of packaging affects the load and unload times as well as the length of tape that can be held in a single reel cartridge there is a takeup reel in the drive while a dual reel cartridge has both takeup and supply reels in the cartridge a tape drive uses one or more precisely controlled motors to wind the tape from one reel to the other passing a read write head as it does citation needed tape cartridges and cassettes were available starting in the mid 1970s and were frequently used with small computer systems with the introduction of the ibm 3480 cartridge in 1984 described as about one fourth the size yet it stored up to 20 percent more data 16 large computer systems started to move away from open reel tapes and towards cartridges 17 the ibm 7340 hypertape drive introduced in 1961 used a large dual reel cassette with a 1 inch wide 2 5 cm tape capable of holding in excess of 40 million six bit characters per cassette depending upon record length 18 a compact cassette from the late 1970s with a game for an apple computer of the era in the 1970s and 1980s audio compact cassettes were frequently used as an inexpensive data storage system for home computers b or in some cases for diagnostics or boot code for larger systems such as the burroughs b1700 20 compact cassettes are logically as well as physically sequential they must be rewound and read from the start to load data early cartridges were available before personal computers had affordable disk drives and could be used as random access devices automatically winding and positioning the tape albeit with access times of many seconds three types of stringy floppy endless loop magnetic tape data storage cartridges in the world of radio broadcasting an analog audio recording product called the fidelipac saw extensive usage from the 1950s through the 1990s this type of cartridge has a continuous loop of tape wound on a special reel that allows tape to be withdrawn from the center of the reel and then wrapped up around the edge the stringy floppy was developed in the late 1970s through the mid 1980s as a data storage product based on the same concept of an endless loop of magnetic tape in a convenient size cartridge notably in an endless loop cartridge the tape can only move forward rewind is not possible in 1984 ibm introduced the 3480 family of single reel cartridges and tape drives which were then manufactured by a number of vendors through at least 2004 initially providing 200 megabytes per cartridge the family capacity increased over time to 2 4 gigabytes per cartridge dlt digital linear tape also a cartridge based tape was available beginning 1984 but as of 2007 future development was stopped in favor of lto citation needed in 2003 ibm introduced the 3592 family to supersede the ibm 3590 while the name is similar there is no compatibility between the 3590 and the 3592 like the 3590 and 3480 before it this tape format has 1 2 inch 13 mm tape spooled into a single reel cartridge initially introduced to support 300 gigabytes the seventh generation drive released in 2023 supports the jf cartridge with a native capacity of 50 terabytes linear tape open lto single reel cartridge was announced in 1997 at 100 gigabytes and in its tenth generation supports 40 terabytes in the same sized cartridge technical details edit linear density edit bytes per inch bpi is the metric for the density at which data is stored on magnetic media the term bpi can refer to bits per inch 21 but more often refers to bytes per inch 22 the term bpi can mean bytes per inch when the tracks of a particular format are byte organized as in nine track tapes 23 tape width edit the width of the media is the primary classification criterion for tape technologies one half inch 13 mm has historically been the most common width of tape for high capacity data storage 24 many other sizes exist and most were developed to either have smaller packaging or higher capacity 25 recording method edit this section does not cite any sources please help improve this section by adding citations to reliable sources unsourced material may be challenged and removed april 2017 learn how and when to remove this message linear recording method is also an important way to classify tape technologies generally falling into two categories linear and scanning citation needed linear edit linear serpentine the linear method arranges data in long parallel tracks that span the length of the tape multiple tape heads simultaneously write parallel tape tracks on a single medium this method was used in early tape drives it is the simplest recording method but also has the lowest data density citation needed a variation on linear technology is linear serpentine recording which uses more tracks than tape heads each head still writes one track at a time after making a pass over the whole length of the tape all heads shift slightly and make another pass in the reverse direction writing another set of tracks this procedure is repeated until all tracks have been read or written by using the linear serpentine method the tape medium can have many more tracks than read write heads compared to simple linear recording using the same tape length and the same number of heads data storage capacity is substantially higher citation needed scanning edit helical scanning recording methods write short dense tracks across the width of the tape medium not along the length tape heads are placed on a drum or disk which rapidly rotates while the relatively slow moving tape passes it citation needed an early method used to get a higher data rate than the prevailing linear method was transverse scan in this method a spinning disk with the tape heads embedded in the outer edge is placed perpendicular to the path of the tape this method is used in ampex s dcrsi instrumentation data recorders and the old ampex quadruplex videotape system another early method was arcuate scan in this method the heads are on the face of a spinning disk which is laid flat against the tape the path of the tape heads forms an arc citation needed helical scan recording writes short dense tracks in a diagonal manner this method is used by virtually all current videotape systems and several data tape formats citation needed block layout and speed matching edit in a typical format data is written to tape in blocks with inter block gaps between them and each block is written in a single operation with the tape running continuously during the write however since the rate at which data is written or read to the tape drive varies as a tape drive usually has to cope with a difference between the rate at which data goes on and off the tape and the rate at which data is supplied or demanded by its host citation needed various methods have been used alone and in combination to cope with this difference if the host cannot keep up with the tape drive transfer rate the tape drive can be stopped backed up and restarted known as shoe shining a large memory buffer can be used to queue the data in the past the host block size affected the data density on tape but on modern drives data is typically organized into fixed sized blocks which may or may not be compressed or encrypted and host block size no longer affects data density on tape modern tape drives offer a speed matching feature where the drive can dynamically decrease the physical tape speed as needed to avoid shoe shining 26 in the past the size of the inter block gap was constant while the size of the data block was based on host block size affecting tape capacity for example on count key data storage on most modern drives this is no longer the case linear tape open type drives use a fixed size block for tape a fixed block architecture independent of the host block size and the inter block gap is variable to assist with speed matching during writes citation needed on drives with compression the compressibility of the data will affect the capacity how sequential access to data edit tape is characterized by sequential access to data similar to punched tape or microfilm the physical nature of a tape on a spool means that to load a specific file the tape must be moved into position under the read head by contrast drum or disk storage allows for much more rapid positioning of read heads random access 27 serpentine tape drives e g qic offer improved access time by switching to the appropriate track tape partitions are used for directory information 28 for some systems metadata such as file name or modification time may not stored modern file archiver and backup tools allow for both compression and retention of metadata on tape backups the linear tape file system is a method of storing file metadata on a separate part of the tape this makes it possible to copy and paste files or directories to a tape as if it were a disk but does not change the fundamental sequential access nature of tape citation needed access time edit tape has a long random access time since the deck must wind an average of one third the tape length to move from one arbitrary position to another tape systems attempt to alleviate the intrinsic long latency either using indexing where a separate lookup table tape directory is maintained which gives the physical tape location for a given data block number a must for serpentine drives or by marking blocks with a tape mark that can be detected while winding the tape at high speed citation needed data compression edit most tape drives now include some kind of lossless data compression there are several algorithms that provide similar results lzw citation needed widely supported idrc exabyte aldc ibm qic and dlz1 dlt citation needed embedded in tape drive hardware these compress a relatively small buffer of data at a time so cannot achieve extremely high compression even of highly redundant data a ratio of 2 1 is typical with some vendors claiming 2 6 1 or 3 1 the ratio actually obtained depends on the nature of the data so the compression ratio cannot be relied upon when specifying the capacity of equipment e g a drive claiming a compressed capacity of 500 gb may not be adequate to back up 500 gb of real data data that is already stored efficiently may not allow any significant compression and a sparse database may offer much larger factors software compression can achieve much better results with sparse data but uses the host computer s processor and can slow the backup if the host computer is unable to compress as fast as the data is written citation needed the compression algorithms used in low end products are not optimally effective and better results may be obtained by turning off hardware compression and using software compression and encryption if desired instead citation needed plain text raw images and database files txt ascii bmp dbf etc typically compress much better than other types of data stored on computer systems by contrast encrypted data and pre compressed data pgp zip jpeg mpeg mp3 etc normally increase in size c if data compression is applied in some cases this data expansion can be as much as 15 citation needed encryption edit standards exist to encrypt tapes 29 encryption is used so that even if a tape is stolen the thieves cannot use the data on the tape key management is crucial to maintain security compression is more efficient if done before encryption as encrypted data cannot be compressed effectively due to the entropy it introduces some enterprise tape drives include hardware that can quickly encrypt data 30 cartridge memory and self identification edit some tape cartridges notably lto cartridges have small associated data storage chips built in to record metadata about the tape such as the type of encoding the size of the storage dates and other information it is also common for tape cartridges to have bar codes on their labels in order to assist an automated tape library 31 viability edit tape remains viable in modern data centers because 32 33 34 it is the lowest cost medium for storing large amounts of data as a removable medium it allows the creation of an air gap that can prevent data from being hacked encrypted or deleted its longevity allows for extended data retention which may be required by regulatory agencies 35 the lowest cost tiers of cloud storage can be supported by tape 35 comparison to disk storage edit tape and disk storage have some important fundamental differences which result in the technologies being used differently in practice one significant difference is how the raw media is packaged with or without the mechanism to use it in disk storage the hard disk drive platters that actually store the data are packaged together with the mechanism that reads and writes to it into a drive while tape media is sold separately from the drive that reads and writes it at scale this has a large impact on cost since expanding capacity does not require paying for additional mechanisms to use it it also simplifies transporting and storing the storage media in recordable surface area as of 2025 a current lto cartridge contains about 20 000 square inches 13 m 2 of surface area while a current hard disk drive of similar capacity with 10 platters only has around 200 square inches 0 13 m 2 of surface area a factor of 100 difference this dramatically affects seek time disks can generally return the first bytes requests within 10 ms but tape can take over 100 sec a factor of 10 000 difference despite the slow seek time of tape streaming throughput can be substantially faster than disk while modern disk commonly have multiple read write heads only one operates at a time tape on the other hand has long had multiple read write heads that operate in parallel modern tape drives have 32 read write elements traversing the tape media at over 3 meters sec total costs get complicated ...