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Linear Tape-Open (or '''LTO''') is a Magnetic Tape Data Storage technology developed as an open alternative to the proprietary Digital Linear Tape (DLT). The technology was developed and initiated by Seagate , Hewlett-Packard , and IBM . The standard Form-factor of LTO technology goes by the name "Ultrium". In the late 1990s, Quantum's DLT and Sony's Advanced Intelligent Tape (AIT) were the leading options for high-capacity, high speed tape storage for PC servers and UNIX systems. Those technologies were and still are tightly controlled by their owners. Consequently, their availability were fairly limited. IBM, HP and Seagate sought to counter this by introducing a more open format. LTO announcement Much of the technology is an extension of the work done by IBM at its Tucson lab during the previous 20 years. IBM storage history . FORM FACTORS LTO technology was designed to come in two form factors, Ultrium and Accelis.
As of 2006, LTO Ultrium is very popular and there are no commercially available LTO Accelis drives or media. In common usage, LTO generally refers only to the Ultrium form factor. Accelis Accelis was developed in 1997 for fast access to data by using a two-reel cartridge that loads at the midpoint of the tape to minimize access time. IBM's (short-lived) 3570 Magstar MP product pioneered this concept. The real-world performance never exceeded that of the Ultrium tape format, so there was never a demand for Accelis. Even Sony has acknowledged the popularity of the single reel, 1/2" form factor by producing the SAIT variant of their AIT technology. Ultrium 1/2" magnetic tape has been used for data storage for more than 50 years. In the mid 1980s, IBM and DEC put this kind of tape into a single reel, enclosed cartridge. IBM called their cartridge 3480 . DEC's DLT was later sold to Quantum. Both technologies have evolved since then and are still widely available. LTO Ultrium was developed as a (more or less) drop-in replacement for DLT. This made it easy for robotic tape library vendors to convert their DLT libraries into LTO libraries. An Ultrium cartridge's dimensions are 102.0 x 105.4 x 21.5 (mm).
GENERATIONS LTO-1
LTO-2
LTO-3
At the full native data rate (80 MB/s), LTO-3 drives can write data faster than most hard disk drives can read. Even the minimum streaming data rate (~30-40 MB/s) is faster than many hard disk drives. LTO-4
Notes
TECHNICAL FEATURES LTO-CM Every LTO cartridge has a Cartridge Memory chip inside it. It is made up of 128 blocks of memory, where each block is 32 Bytes for a total of 4096 Bytes. This memory can be read and/or written, 1 block at a time, via a ''non contacting passive RF interface.'' This memory is used to identify tapes and to help drives discriminate between the different generations of the technology. Every LTO drive has a CM Reader in it. External readers are available, both built into tape libraries and handheld. The non-contact interface has a range of 20 mm. Fujitsu Cartridge Memory documentation LTO-DC The LTO specification describes a Data Compression method LTO-DC. This is the same as the method described by Sony in their AIT-3 specification. It used the algorithm ALDC IBM ALDC documentation which is a variation of LZS. In addition, LTO-DC is designed so that it does not apply the compression to uncompressible data (ie. data that is already compressed or sufficiently random to defeat the compression algorithm). LZS is a patent-encumbered algorithm, controlled by Hi/Fn. Patent claim by Hi/Fn LTO-DC achieves an approximately 2:1 compression ratio when applied to the Calgary Corpus . This is inferior to slower algorithms such as Bzip2 , but similar to the high speed algorithms built into other tape drives. It should be noted that 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. In contrast, encrypted data and pre-compressed data (PGP, ZIP, JPEG, MPEG, MP3, etc.) would normally increase in size if compression was attempted. This expansion on tape is prevented by the LTO tape drive's detection of uncompressible data. Positioning Times Maximum rewind time is 98 seconds. Note that due to the back and forth writing, rewinding rarely takes this long. If a tape is written to full capacity, there is no rewind time, since the last pass is a reverse pass leaving the head at the beginning of the tape. Average tape seek/filemark search time is 75 seconds. Reliability The tapes contain a strong error correction algorithm that makes data recovery possible when lost data is within one track or up to 32 mm of the tape medium. Tape Durability ''Estimated''
Tape Layout LTO Ultrium tape is laid out with 4 data bands sandwiched between 5 servo bands. The data bands are numbered 3,1,0,2 across the tape and are filled individually, in numeric order. The head unit straddles the 2 servo bands that border the data band that is being written or read. Data tracks are written in forward and reverse passes, also called wraps. It takes several wraps to completely fill a data band. All of the write elements in the head write simultaneously as the head passes over the data band from the physical start of the tape to the physical end. This makes one forward wrap. At the end, the head shifts to line up the write elements with a new set of tracks within the same data band. It is now ready to make a reverse wrap. All tracks written by the same write element in the same direction are grouped together. This leads to a set of serpentine patterns in each data band. The servo bands are used to keep the head precisely aligned within the data band. To determine the number of passes required to fill up a tape, divide the total number of tracks by the number of write elements. For example, an LTO-2 tape requires 64 passes. The block structure of the tape is logical so inter block gaps, file marks, tape marks and so forth take only a few bytes each. In LTO-1 this logical structure has CRC codes and compression added to create blocks of 403884 bytes. Another chunk of 468 bytes of information (including statistics and information about the drive that wrote the data and when it was written) is then added to create a 'dataset'. Finally error correction bytes are added to bring the total size of the dataset to 491520 bytes before it is written in a specific format across the eight heads. The formats for LTO-2 and LTO-3 are similar. When data is written to the tape it is verified by reading it back using the read heads that are positioned just 'behind' the write heads. This allows the drive to write a second copy of any data that fails the verify without the help of the host system. WORM New for LTO-3 is Write Once Read Many (WORM) capability. This is normally only useful for legal record keeping. An LTO-3 drive will not erase or overwrite data on a WORM cartridge, but will read it. An LTO-3 WORM Cartridge is identical to a normal LTO-3 tape cartridge except its LTO-CM chip identifies it to the drive as WORM. There is nothing different about the tape medium in a WORM cartridge. Typically the WORM cartridges have a different color packaging. CAUTION Cleaning Normal cleaning cartridges are abrasive and frequent use will shorten the drive's lifespan. HP LTO drives have a fancy cleaning strategy HP cleaning strategy that will prevent the drive from actually using the cleaning tape if it is not needed. There is an internal mechanism that also handles cleaning tasks based on error rate criteria and time. The internal tape head cleaner is also activated when the cleaning cartridge is loaded. Erasing The magnetic servo tracks on the tape are factory encoded. Using a bulk eraser (or otherwise exposing the cartridge to a strong magnetic field) will erase the servo tracks along with the data tracks and make the cartridge '''unusable'''. MECHANISMS Current Compliance-Verified licensed manufacturers of LTO technology mechanisms are IBM , Hewlett-Packard , Quantum , and Tandberg Storage . LTO licensees CARTRIDGES Compliance-Verified licensed manufacturers of LTO technology media are Maxell , TDK , Imation , EMTEC , Fujifilm , and Sony . LTO licensees All other brands of media are manufactured by these companies under contract. Since its bankruptcy in 2003, EMTEC no longer makes LTO media products. Linear Tape-Open (LTO) Technology Continues Licensee Momentum with Signing of Fujitsu and Quantegy both licensed LTO technology, but never produced compliance-verified media. Colors The colors of LTO Ultrium cartridge shells are somewhat standardized. HP is the notable exception.
Labels The LTO cartridge label uses the bar code symbology of USS-39 . A description and definition is available from the Automatic Identification Manufacturers (AIM) specification Uniform Symbol Specification (USS-39) and the ANSI MH10.8M-1993 ANSI Barcode specification. SALES FIGURES
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