LTO, or Linear Tape-Open, is a format of data storage tape that is widely used all around the world.
LTO, at the moment, is the most popular data tape format mainly due to its massive storage size, with the latest iteration (LTO-9) capable of holding 18 terabytes of data in a single tape. However, LTO is also highly scalable and adaptable.
In this guide to LTO tapes, we will learn all you need to know about the LTO tape format, including:
Without further ado, let us begin with the basics: what is LTO?
LTO stands for Linear Tape-Open, and is a format (or technology) of magnetic data tape storage developed in the late 1990s by IBM, HP, and Seagate (that formed the LTO Consortium. LTO is designed as an open standard, and the standard form-factor of the LTO technology is called Ultrium (hence, LTO Ultrium.)
The magnetic data tape storage technology has actually been around since the 1950s, with the half-inch magnetic tape, IBM 7 track, and later IBM 9 track being the pioneering data tape format back then.
The medium continued to evolve until the late 1990s. By then, Quantum’s Digital Linear Tape (DLT) and Sony’s Advanced Intelligent Tape (AIT) were the two leading options for high-capacity data tape storage for PC servers and enterprise-grade UNIV systems. Both formats were tightly controlled by their owners, so there was practically no competition, driving their prices high.
The LTO Consortium was formed by IBM, HP, and Seagate to add more competition to this market, and the initial plan was to launch to LTO formats: Ultrium, planned as a single-reel, half-inch tape and Accelis with 8mm tape on dual reels. The plan was to optimize Ultrium for capacity and Accelis for speed and low latency. However, only Ultrium was ever produced for the mass markets.
LTO Ultrium has grown to be a very popular data storage tape format. In 2000, the first iteration of Ultrium was introduced with a 100 GB native capacity, although initially, it was going to be available with 10 GB, 30 GB, and 50 GB cartridges too, but scrapped.
As of 2021, there are nine generations of LTO Ultrium tapes (LTO-1 to LTO-9) commercially available in the market, and five more (LTO-10 to LTO-14) are planned.
You can see the details and differences between these different LTO formats in the table below:
|Format||Release Date||Uncompressed Capacity||Compressed Capacity||Max Compressed Speed (MB/s)||Max Uncommpressed Speed (MB/s)||Time needed to write a full tape at maximum speed (hh:mm)|
|LTO-1||2000||100 GB||200 GB||20||40||1:23|
|LTO-2||2003||200 GB||400 GB||40||80||1:23|
|LTO-3||2005||400 GB||800 GB||80||160||1:23|
|LTO-4||2007||800 GB||1.6 TB||120||240||1:51|
|LTO-5||2010||1.5 TB||3.0 TB||140||280||3:10|
|LTO-6||2012||2.5 TB||6.25 TB||160||400||4:20|
|LTO-7||2015||6.0 TB||15.0 TB||300||750||5:33|
|Type M (M8)||2017||9.0 TB||22.5 TB||300||750||8:20|
|LTO-8||2017||12.0 TB||30.0 TB||360||900||9:16|
|LTO-9||2021||18.0 TB||45.0 TB||400||1,000||12:30|
|LTO-10||TBA||36.0 TB||90.0 TB||1,100||2,750||12:07|
|LTO-11||TBA||72.0 TB||180.0 TB||TBA||TBA||TBA|
|LTO-12||TBA||144.0 TB||360.0 TB||TBA||TBA||TBA|
|LTO-13||TBA||288.0 TB||720.0 TB||TBA||TBA||TBA|
|LTO-14||TBA||576.0 TB||1,440 TB||TBA||TBA||TBA|
Note: “Type M (M8)” refers to how some LTO-8 drives may write previously unused LTO-7 tapes with an increased, uncompressed capacity of 9 TB. Once this cartridge is initialized as Type M, it may not be changed back into a standard LTO-7 cartridge.
Unlike other storage tape technologies, a Ultrium cartridge can only be used by a particular generation of LTO drive (with the exception of Type M or M8, as discussed above,) with the following rules:
As a storage tape, an LTO tape reads and writes data in a sequential manner—one file after another—as opposed to hard disk drives (HDDs) and solid-state drives (SSDs) that write and read data in a non-sequential way by using rotating disks.
This sequential storage method, however, means the system must start at the beginning of the tape and roll through it to read specific data or write new data. Naturally, this mechanism results in slower read/write speeds than HDDs or SSDs. However, today’s technologies—especially LTO’s advanced linear tape technology—offer similar drive performance to HDDs and SSDs.
Today, there are two primary tape technologies used in the market: linear tape (that is used by LTO) and helical scan.
A helical system writes data in diagonal strips along the tape. To achieve this, two tape reels with quarter-inch-wide tape media are used in the same cartridge. The helical scan technology offers a higher data storage density than linear tape but typically stores less overall data than linear tapes
The linear tape model, however, uses a much different method to read/write data, so these two formats are largely incompatible with each other despite offering comparable performances.
A linear tape (including LTO), on the other hand, has multiple read/write heads reading and writing data along parallel tracks of data that extend the length of the tape. Linear tape media is typically around a half-inch wide, and each tape cartridge only has one tape spool.
LTO tapes are made up of narrower servo bands and wider data bands. To be more exact, each tape has four data bands sandwiched between five servo bands.
In such configurations, the servo bands act like guard rails for the read/write head or heads. The read/write head positions itself between two servo bands, ensuring compatibility and adjustments between different LTO tape drives. The magnetic servos will also play their parts in error correction and hardware data compression.
Each LTO tape head has either 8, 16, or 32 read/write head elements and 2 servo read elements. If it has 8 head elements, then it has 8 tracks, and the set of 8, 6, or 32 tracks are written or read in a one-way end-to-end pass. In this configuration, the tape head shifts laterally to access different tracks within each band and possibly to also access other bands. This set of tracks (8,16, or 32) is called a “wrap.”
LTO-6 and newer tapes have 32 read/write head elements, and so can read or write 32 tracks simultaneously.
Assuming it’s a completely blank, brand-new LTO tape, data writing starts at wrap 0, band 0. The wrap 0 runs from the beginning of the tape (BOT) to the end of the tape (EOT), so this is called a forward wrap. The next sequential wrap (band 0, wrap 1) is a reverse wrap running from EOT to BOT while also including a track that runs along one side of the data band.
This sequence continues in different wraps, alternating between forward and reverse passes with slight shifts toward the middle of the band on each pass. In such a pattern, the tracks written on each pass partially overlap the tracks written on the previous wrap in the same direction.
This back-and-forth alternating pattern runs from the edges of the tape into the middle and looks like a coiled snake, and thus is often known as linear serpentine recording. The linear serpentine procedure is repeated until all tracks and bands have been read or written as needed, and this method allows the tape to have more tracks than rear/write head elements, thus allowing for a substantially higher data storage capacity than the standard linear recording procedure.
One of the drawbacks of storage tapes (including LTO Tapes) is the condition we call shoe shining.
Tape drives spin rapidly, and when the drive finds the data it needs to access, the tape must physically stop and go back to the point where the data is, and this process can be repeated a few times (in a very fast manner) until the right location is met. This start, stop, and backup motion resembles the back-and-forth movement of shining a shoe (hence the name.)
Too many shoe-shining motions can wear out both the tape drive and the cartridge, shortening the life span of both. Also, repeated shoe-shining alone can slow the drive’s read/write time.
To tackle this shoe-shining issue, newer LTO tapes adopt a built-in speed-matching (or auto speed) mechanism to lower the movement speed when needed and maintain a constant speed. In LTO-8 tapes, the auto (matched) speed ranges between 112 and 360 MB/s.
LTO offers several specific mechanisms in place to offer advanced levels of built-in security.
To date, LTO tapes offer a much lower level of bit-error-rate (BER) than HDDs and SSDs. LTO-7 and LTO-8 tapes offer a BER of 1 x 10-19. Meaning, a typical LTO-8 tape will have one bit error in over 10 exabytes of data, or 1 bit error in more than 800,000 LTO-8 tapes. In comparison, a typical HDD has a BER of HDDs (1 x 10-15).
To ensure that the data written on the tape is accurate and identical to what’s intended, an after-write verification process is used. This is mainly achieved by using the error-correcting code (ECC) on the headers, which is a mandatory part of the recording format on the tape.
Magnetic tape has been used as a data storage solution for decades, dating back to the 1950s. Thus, it’s easy to overlook storage tapes, including LTO tapes, as old and obsolete.
However, while LTO tapes may not offer the excitement of new SSD or cloud options, they do offer several unique benefits over other formats, especially as a long-term archiving medium.
While HDDs and SSDs offer higher read/write speeds than LTO tapes, LTO tapes offer a longer life span, a much lower error rate, and easier maintenance. This makes LTO tapes ideal for long-term archiving when the lower drive speeds won’t be much of an issue.
Below are some key benefits offered by LTO tapes over other formats
LTO Tapes offer an unmatched shelf life of more than 30 years, making them an ideal choice for long-term archiving. Today’s technologies also ensure it’s easy to find files stored in LTO tapes years and even decades after they were archived.
In comparison, HDDs have a life expectancy of only 5 years on average, with a higher failure rate.
Keep in mind, however, that the 30-year lifespan prediction would require the LTO tape to be stored in an optimal and controlled environment with regulated temperature (18°C) and humidity (40%).
At the moment, magnetic tapes, including LTO tapes, offer the lowest price per TB over other mediums.
However, when it comes to calculating storage costs, it’s important to consider various factors that would contribute to the total cost of ownership of the LTO tapes, including:
Even after taking all these factors into account, including off-site storage cost, storage tapes remain the least expensive storage choice at the moment. This is because the cost per TB (or per GB) drops the more data you store on the LTO tape, which we will discuss below.
Another key highlight of LTO storage tapes is their storage capacity, with the current LTO-8 offering 12 TB uncompressed/native capacity per cartridge.
With files (especially photos and videos) only getting larger and larger, the storage capacity of LTO tapes will become even more valuable.
An advantage that’s often overlooked is the fact that LTO tapes’ read performance for large files is better than HDDs. LTO-8 tapes offer around 360MB/s for uncompressed data reading, while traditional HDDs only offer 200 to 200 MB/s.
LTO, as we know, stands for Linear Tape Open, with Open here referring to ‘open standards.’
LTO’s open format is actually an advantage on its own. Since the technology is available for license by multiple vendors, the LTO format doesn’t hinge on the success or failure of one manufacturer alone, and the competition between these different manufacturers drives the price low (and quality in check.)
In short, the open format will keep LTO tapes competitively priced and constantly updated.
The LTO Consortium (IBM, Hewlett Packard, and Certance) has published a roadmap with predicted specifications for future generations of LTO tapes up to LTO-14, making obsolescence more manageable.
Portability and security
Another important advantage of the LTO storage tape, especially as a long-term archive medium, is its portability. It’s actually much safer to transport LTO tapes than HDDs with their vulnerable motorized parts.
Also, since we can store tape cartridges 100% offline, they are safe from cyberattacks that rely on internet connectivity, as well as from accidental deletion, glitches, and other issues common in connected HDDs and SSDs.
It’s also worth noting that it’s relatively easy to implement encryption on LTO tape cartridges. Since LTO-4, users can encrypt data before it is written to tape with Application Managed Encryption (AME). All current LTO manufacturers support AME.
As we can see, there are many benefits of the LTO tape format (and storage tapes in general) over HDDs, SSDs, and other mediums. Yet, it doesn’t mean LTO is a perfect medium without any weaknesses at all.
Here are some drawbacks to consider before investing in LTO tapes as your storage solutions:
Maintenance and management
LTO tape drives must be stored in a room with controlled temperature and humidity, which may translate into additional costs and maintenance challenges. Also, LTO drives have mechanical parts that need to be cleaned and adjusted from time to time.
Meaning, if you decide to invest in LTO tapes, make sure to plan regular maintenance periods to ensure their longevity. This will also translate into the need to invest inexperienced manpower with adequate technical knowledge.
You’ll need an experienced admin that can also help you in lifecycle management and decide when to upgrade and plan regular migrations.
LTO tapes are sequential access media. Meaning, they must start at the beginning of the tape and roll through it to write new data or read specific data. This causes the LTO tapes to be slower than HDDs when it comes to reading data in random order, and when this happens frequently, it may cause wear out of both the tape cartridge and the drive.
However, speed is not a deal breaker in LTO tapes, especially considering we’ll mainly use LTO for long-term archiving when speed isn’t too much of an issue. When storing larger files—including media files—, random-access speed is also less relevant.
We have briefly discussed how excessive shoe-shining can shorten the lifespan of both the LTO drive and cartridge. While newer LTO tapes have built-in speed matching function to tackle this issue, this can still be a concern.
In LTO tapes, data to be stored is typically accumulated in buffers first before being streamed onto the tape.
In such a configuration, when the buffer is not full, the tape may be stopped abruptly, positioning itself for the next delivery of data from the buffer. When this happens frequently, it can lower the LTO system’s overall speed.
A single drive for multiple tapes
Unlike HDDs or SSDs, when dealing with massive data catalogs, we have to eject and replace the LTO tape cartridges as needed.
In practice, we will need to perform this manually (which can be challenging and time-consuming), or invest in a tape library, where a robot arm fetches and replaces the cartridges into the drives (which translates into additional costs.)
While LTO tapes are naturally very durable, they do have mechanical moving parts that are subject to wear and tear and magnetic damage.
Thus, it’s important to perform proper storage and maintenance to ensure longevity.
Here are some best practices to follow:
LTO tapes remain one of the most cost-effective storage mediums. While it doesn’t have the speed of HDDs and SSDs (although it’s not that far behind), it has the lowest cost per GB than other mediums, making it ideal for long-term digital archiving.
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