Linear Tape-Open
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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".
Current Compliance-Verified licensed manufacturers of LTO technology mechanisms and/or media are IBM, Hewlett-Packard, Quantum, Maxell, Tandberg Storage, TDK, Imation, EMTEC, Fujifilm, and Sony. [1]
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[edit] Origins
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.[2] Much of the technology is an extension of the work done by IBM at its Tucson lab during the previous 20 years.[3]
[edit] Form Factors
LTO technology was designed to come in two form factors, Ultrium and Accelis.
- Accelis -- 8 mm tape, dual reel cartridge, biased toward fast access time, very similar to Sony's AIT product.
- Ultrium -- 1/2" tape, single reel cartridge, biased toward high capacity, very similar to Quantum's DLT product and IBM's 3590 Magstar product.
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.
[edit] 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.
[edit] Ultrium
1/2" magnetic tape has been used for data storage for more than 50 years. In the mid 1980's, 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).
- An Ultrium drive is expected to read data from a cartridge in its own generation and at least the two prior generations.
- An Ultrium drive is expected to write data to a cartridge in its own generation and to a cartridge from the immediate prior generation in the prior generation format.
[edit] Generations
| Generation | LTO-1 | LTO-2 | LTO-3 | LTO-4 | LTO-5 | LTO-6 |
|---|---|---|---|---|---|---|
| Release Date | 2000 | 2002 | 2005 | 2007 | TBA | TBA |
| Native Data Capacity | 100 GB | 200 GB | 400 GB | 800 GB | 1.6 TB | 3.2 TB |
| Max Speed (MB/s) | 20 | 40 | 80 | 120 | 180 | 270 |
| WORM Capable? | NO | NO | YES | YES | PLANNED | PLANNED |
| Tape Thickness | 8.9 um | 8.9 um | 8 um | 8 um? | ||
| Tape Length | 609 m | 609 m | 680 m | 680 m? | ||
| Tape Tracks | 384 | 512 | 704 | 1024 | ||
| Write Elements | 8 | 8 | 16 | 16? | ||
| Wraps per Band | 12 | 16 | 11 | 16? | ||
| Linear Density (bits/mm) | 4880 | 7398 | 9638 | 13300? | ||
| Encoding | RLL 1,7 | PRML | PRML | PRML? |
[edit] LTO-1
- Originally designed to come in 4 lengths of tape: 10, 30, 50, and 100 GB.
- Uses the same data compression as AIT
- Tape encoding is RLL 1,7
- Bit density is low, compared to second and third generations.
The LTO-1 (Ultrium-1) tape format was a quick to market design with a strong view to the future. Because it was quick to market the original LTO-1 was created using easy technology.
[edit] LTO-2
- Doubled capacity and transfer speed
- Switched to PRML encoding
[edit] LTO-3
- Doubled capacity and transfer speed again
- Introduced WORM feature
- Doubled number of write elements in head
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.
[edit] LTO-4
- Specification released to licensees on 11th January 2007 [4]
- Products based on LTO-4 expected in the first half of 2007.
- Doubled capacity again to 800 GB.
- Added drive level encryption.
- Increase data transfer rate by 50% to 120 MB/s.
[edit] Notes
- Data Capacity and Speed figures above are for uncompressed data. Most manufacturers list compressed capacities on their marketing material. Capacities are often stated on tapes as double the actual value; they assume that data will be compressed with a 2:1 ratio (IBM uses a 3:1 compression ratio in the documentation for its Mainframe tape drives. Sony uses a 2.6:1 ratio for SAIT). See LTO-DC below. The marketing material also uses non-computer definitions for bytes capacities.
- The units in this section are as follows:
- B = byte(s) = 8 bits
- KB = kilobyte(s) = 103 bytes
- MB = megabyte(s) = 106 bytes
- GB = gigabyte(s) = 109 bytes
- TB = terabyte(s) = 1012 bytes
- m = meter(s)
- mm = millimeter(s) = 1 m / 1,000
- um = micrometer(s) = 1 m / 1,000,000
- Minimum and maximum reading and writing speeds are drive dependent.
- Tape speed adjusts to available data stream, within the minimum and maximum streaming speeds.
[edit] Technical Features
[edit] 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. [5]
[edit] 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 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. [6]
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 uncompressable data.
[edit] Positioning Times
Maximum rewind time is 98 seconds. Note 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 75 seconds.
[edit] 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.
[edit] Tape Durability
Estimated
- 1 million passes (NOTE: many passes are required to fill up a tape)
- 30 years of archival storage
- 20000 loads and unloads
[edit] 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.
[edit] WORM
New for LTO-3 is 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.
[edit] Caution
[edit] Cleaning
Normal cleaning cartridges are abrasive and frequent use will shorten the drive's lifespan. HP LTO drives have a fancy cleaning strategy [7] 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.
[edit] Erasing
The servo tracks on the tape are magnetically encoded. Using a bulk eraser (or otherwise exposing the cartridge to a strong magnetic field) will ruin the cartridge!
[edit] Cartridge Colors
The colors of LTO Ultrium cartridge shells are somewhat standardized. HP is the notable exception.
| Manufacturer | Type | Color | Part Number | Notes |
|---|---|---|---|---|
| FujiFilm | UCC | 26200014 | ||
| HP | UCC | Orange | C7978A | |
| IBM | UCC | 35L2806 | ||
| Maxell | UCC | Gray | 183804 | |
| Quantum | UCC | Black | MR-LUCQN-01 | |
| Sony | UCC | LTXCLWW | ||
| Tandberg | UCC | Grey | 0043 2631 | |
| TDK | UCC | Gray | ||
| EMTEC / RPS | LTO-1 | Black | 547247 | |
| FujiFilm | LTO-1 | Black | 26200010 | |
| HP | LTO-1 | Blue | C7971A | |
| IBM | LTO-1 | Black | 08L9120 | |
| Imation | LTO-1 | Black | 51122-41089 | |
| Maxell | LTO-1 | Black | 183800 | |
| Quantum | LTO-1 | Black | MR-L1MQN-01 | |
| Sony | LTO-1 | Black | LTX100G | |
| StorageTek | LTO-1 | MEDLTO1-003 | Pre-labeled in series with colour/barcodes | |
| Tandberg | LTO-1 | Black | 0043 2630-1 | |
| TDK | LTO-1 | Black | D2404 100 | |
| EMTEC / RPS | LTO-2 | Purple | 547249 | |
| FujiFilm | LTO-2 | Purple | 26220001 | |
| HP | LTO-2 | Dark Red | C7972A | |
| IBM | LTO-2 | Purple | 08L9870 | |
| Imation | LTO-2 | Purple | 51122-16598 | |
| Maxell | LTO-2 | Purple | 183850 | |
| Quantum | LTO-2 | Purple | MR-L2MQN-01 | |
| Sony | LTO-2 | Purple | LTX200G | |
| StorageTek | LTO-2 | Purple | MEDLTO2-008 | Pre-labeled in series with colour/barcodes |
| Tandberg | LTO-2 | Purple | 0043 2744 | |
| TDK | LTO-2 | Purple | D2405 200 | |
| FujiFilm | LTO-3 | Slate-Blue | 26230010 | |
| HP | LTO-3 | Yellow | C7973A | |
| IBM | LTO-3 | Slate Blue | 24R1922 | |
| Imation | LTO-3 | Blue-Gray | 51122-17532 | |
| Maxell | LTO-3 | Blue-Gray | 183900 | |
| Quantum | LTO-3 | Blue | MR-L3MQN-01 | |
| Sony | LTO-3 | Gray | LTX400G | |
| StorageTek | LTO-3 | MEDLTO3-004 | Pre-labeled in series with colour/barcodes | |
| Tandberg | LTO-3 | Blue-Gray | 0043 3216 | |
| TDK | LTO-3 | Blue-Gray | D2406 400 | |
| FujiFilm | LTO-3 WORM | Slate-Blue / Platinum | 26230014 | |
| HP | LTO-3 WORM | Yellow & Gray | C7973W | |
| IBM | LTO-3 WORM | Slate Blue & Platinum | 96P1203 | |
| Maxell | LTO-3 WORM | Blue-Gray/Gray | 183950 | |
| Quantum | LTO-3 WORM | Blue/Gray | MR-L3MQN-02 | |
| Sony | LTO-3 WORM | LTX300W | ||
| TDK | LTO-3 WORM | Blue-Gray & Light Gray | D2406W 400 |
- UCC means Universal Cleaning Cartridge, which works with LTO-1, LTO-2, and LTO-3 drives.
- Different manufactures use different names for the same color sometimes. The names in the table above come from the manufacturers' documentation.
- WORM cartridges are two-tone, the top half of the shell is the normal color of that generation for that manufacturer, and the bottom half of the shell is a light gray.
[edit] Sales Figures
| Year | Drives Sold | Media Sold |
|---|---|---|
| 2002 | 175,000 | |
| 2003 | 262,000 | |
| 2004 | 354,000 | |
| 2005 | 461,000 |
- In September 2006, the LTO consortium announced [8] that over 1.5 million LTO drives and 50 million LTO cartridges have shipped.
- In 2005, the LTO Program reached the milestone of more than 1 million tape drives shipped and more than 30 million tape cartridges shipped since September 2000, when products based on the format first became commercially available.
- In July 2003, LTO Program announced 350,000 drives sold and 10 million cartridges sold since Sept. 2000 (date first available).
- in 2002 LTO outships SDLT by nearly 2 to 1. Sales since then have dominated other "super" formats (SDLT, SAIT).
- Some sales data from Freeman Reports [9] and the LTO consortium [10].
[edit] External links
- IBM's LTO RedBook - EVERYTHING you wanted to know...
- Linear Tape Open - Consortium Homepage
- Tandberg drive manual with lots of generic details
- ECMA 319 -- Specification of Ultrium 1 [11]
- ECMA 321 -- Specification of SLDC [12]
[edit] See also
| Magnetic tape data storage formats | ||
|---|---|---|
| Linear | Helical-Scan | |
| Three Quarter Inch (~19 mm) |
||
| Half Inch (12.65 mm) |
UNISERVO (1951) - IBM 7 Track (1952) - 9 Track (1964) - IBM 3480 (1984) - DLT (1984) - IBM 3590 (1995) - T9840 (1998) - T9940 (2000) - LTO Ultrium (2000) - T10000 (2006) |
Redwood SD-3 (1995) - DTF (19xx) - SAIT (2003) |
| Eight Millimeter (8 mm) |
Travan (1995) - IBM 3570 MP (1997) |
|
| Quarter Inch (6.35 mm) |
||
| Eighth Inch (3.81 mm) |
KC Standard, Compact Cassette (1975) - DC100 (1976) - Datassette (1977) - DECtapeII (1979) |
DDS/DAT (1989) |
| Stringy (1.58 - 1.9 mm) |
Exatron Stringy Floppy (1979) - ZX Microdrive (1983) - Rotronics Wafadrive (1984) |
|
