August 2, 2004
There are many popular tape formats used for computer storage. At the present time, the three most popular formats seem to be DLT, 8mm, and 4mm. Of course, each of these formats is completely incompatible, and considerable incompatibilities often exist within any one form factor.
The purpose of this document is to provide information on the history and background of the tape drives made by the Exabyte corporation in the 8mm form factor. When one encounters a tape drive in this family it's not always obvious what tapes should be used with it, what its capabilities are, etc.. This document is intended to be an introduction to these tape drives.
One thing to note: In 1996 Sony created the Advanced Intelligent Tape (AIT) system. AIT drives are 8mm tape drives that use Advanced Metal Evaporated (AME, see the Tapes section below) 8mm tapes in a format that is completely incompatible with Exabyte drives. That's fine, there's nothing wrong with AIT tape systems. Many people use them and are very happy with them. They're not the topic of this document, and these drives should not be confused with Exabyte drives, just because they use the same media as some Exabyte products. However, these drives exist and people should be aware of the difference. If an 8mm tape drive indicates that it is made by Sony or includes the abbreviation "AIT", it's a different beast than the Exabyte drives that are discussed here.
Note also that historically that Exabyte has played around with tape drives using tape form factors that are not 8mm. Perhaps most confusingly, Exabyte briefly produced 4mm tape drive models, the EXB-4200 and EXB-4200c. However, this document does not consider these "diversions".
8mm tape drives are shipped under the labels of many manufacturers. Sun, SGI, IBM, and others have sold Exabyte-compatible tapes under their own banners. However, the reason these drives are all Exabyte-compatible is that their innards were all made by Exabyte. In fact, all 8mm data tape drives that are not AIT are made by Exabyte.
Exabyte has made several models that are not listed here. However, these are the main families of drive electronics. Their other stand alone 8mm drives are typically going to have the same characteristics of one of the drives listed here. Also, I don't discuss tape libraries here. Exabyte has produced robotic tape juke boxes of various capacities using many types of drive motors. These devices aren't discussed here. This document is concerned with the drive electronics, its characteristics, and what media can be used with it.
In 1987, Exabyte released the EXB-8200, their first 8mm helical scan drive. The 8200 was capable of storing approximately 2 GB of data on 112m tapes. The 8200 fit in 5 1/4" by full-height (3 1/2" high) drive bays and used commonly available Metal Particle (MP) 8mm tapes, essentially the same formulation and mechanisms used by commercial 8mm video recorders.
In about 1993 the EXB-8500 was released in approximately the same form factor. This drive supported the same tapes and could store up to 5 GB of data.
After the 8500, the next drive to hit the market was the EXB-8505. This was the first half-height (1 3/4" high) 8mm drive Exabyte produced. I believe it had the same capacity as the 8500, but it was now available in a smaller form factor. I believe it was released in about 1994.
In short order the 8505 was followed by the 8505XL which was basically the same drive, but it now supported the longer 160m XL tapes, increasing backup capacity to 7 GB uncompressed, and a nominal 14 GB of compressed data.
Also released was the 8505c, which was the same as the 8505, but had internal logic to increase the amount of data that could be stored on a tape by performing software compression of data.
Now would be a reasonable time to take a little digression to talk about tape drive compression. Ostensibly, compression increases the capacity of tape drives by compressing the data as it comes from disk before it hits the tape. There are two problems with this.
First, there can be no guarantee that the data being stored is compressible. If you're storing huge text files or files that contain nothing but zeros, this can be a big help. However, it is my experience that for most mixed data sets that the compression available in Exabyte drives improves tape capacity only marginally.
Second, even if compression improves tape capacity it is awfully difficult to predict what capacity a tape will have if one is backing up a data set that varies from backup to backup. Guess wrong and you're unattended backup hangs waiting for someone to replace the tape. No good. It's not always practical, but I like to size my backups so that the data set will fit on the backup medium even in the absence of compression. Then compression ends up being a bonus that reduces wear on the tape and tape heads, and allows the backups to finish in less time.
For those tape drives that support compression, Exabyte usually lists two capacities. The first is the "uncompressed" capacity, the second (always twice the first value) represents their "estimated" compressed capacity. I've found their first number to be pretty reliable, although it relies on the use of the longest tape compatible with that drive. Compressed capacities vary significantly with the characteristics of the data stored. Consequently, I've found the second number to be mostly useless, except that it tells the consumer that some sort of compression is supported.
In the same format as the 8505, Exabyte also shipped the 8205 and 8205XL. The difference between these two drives was that the XL supported 160m tapes whereas the 8205 did not. Frankly, I'm not entirely sure about the capacity of the 8205, but I'd guess it was the same as the 8200, 2 GB. If this is the case, then it would stand to reason that the 8205XL would be able to record about a 3 GB on each XL tape.
Next, Exabyte released the 8700 series of tape drives. These were lower priced than the 85xx drives and seemed to be aimed more at the consumer market. These were the only Exabyte drives not shipped optionally with or without external enclosures. Since these drives were top loading, they were all external drives.
It seems to me that the 8700 was a bit of a flop as a product. It was still too expensive for most home use, and at the same time it was too awkward to be used in data centers. Nonetheless, these are reasonable drives. One I purchased in 1998 worked admirably until it needed repairs after six years of continual use. Not too shabby for electronics equipment with moving parts.
The 8700 was followed by the Eliant 820, which I believe is also known as the 8705. What was the difference between this device and the 8505XL? As far as I can tell, the only difference in in data transfer speeds. The Eliant is supposed to be a little faster.
1996 represented a significant shift for Exabyte. While they continued to sell their previous drive models, they also released their next generation 8mm drive named "Mammoth". The first generation Mammoth could support a whopping 20 GB of uncompressed data. The big down side is that while it still used 8mm tape, it was no longer acceptable to use the old 112m and 160m XL MP tapes with this new drive. Instead, tapes using the Advanced Metal Evaporated (AME) tape technology were required. MP tapes could still be read by a Mammoth drive, but because the magnetic material could flake off and clog the drive heads, it was required that Mammoth drives be cleaned after every time non-AME tapes were read, and it was never a good idea to try to write to non-AME tapes. I'm not sure that was even allowed. I never tried it and I don't recommend it.
The first generation Mammoth was also known as the EXB-8900. It came in a form factor very similar to that of the 8505. Some 8900s shipped with an LCD panel underneath the tape loading area that could display limited diagnostic information about the drive. Some 8900s did not have this feature. The Mammoth could use AME tapes of up to 170m length. There was also the Exabyte Mammoth-LT, which seems to have been a budget version of the 8900. It didn't have an LCD display and could only handle AME tapes of up to 125m in length. I believe it's capacity was listed as 14 GB uncompressed.
The next generation of Exabyte drive is known as the Mammoth-2. As far as I know, this is the first Exabyte 8mm drive to not be given an 8xxx model number. Of course, this isn't surprising since the 8900 pretty much ended that naming convention. Like the Mammoth, this drive introduced yet another new generation of tape media which Exabyte calls "AME with SmartClean"(TM). The Mammoth-2 can use regular AME media, but this is not recommended, although the consequences are not quite as dire as if an 8900 were to use old Metal Particle (MP) tapes. The Mammoth-2 stores 30 GB of uncompressed data on a 225m AME with SmartClean tape. All Mammoth-2s have display LCDs on their front panel.
After Mammoth-2 comes the VXA-1. Again, the tape media change to "V17" (170m) VXAtape(TM) cartridges. These hold 33 GB of uncompressed data. Naturally enough, this was followed by the VXA-2. These use the same media, but tape lengths can be increased to 230m using the V23 cartridge. This allows a maximum uncompressed capacity of a whopping 80 GB on a single tape. VXA drives use a different encoding method, so I expect that they could not read data written by Mammoth tapes. I do not know if VXA drives can read or write to AME tapes, but I would expect not. It's almost certainly not a good idea to try. Despite the extra capacity, it's worth noting that VXA drives are considerably less expensive than Mammoth-2 drives.
Scheduled for release in 2005 will be the VXA-3. Using the same VXA media, Exabyte projects that storage of 160 GB uncompressed will be possible with these systems. This represents the current extent of Exabyte's 8mm product line.
Besides drive capacities and costs, media considerations are critical when formulating a backup strategy. Some tape length and composition considerations were mentioned accompanying descriptions of appropriate drive models in the preceding section, but there's more to know about 8mm data tape history.
Exabyte recommended the use of "data grade" cartridges with their early models, namely the 8200 and 85xx series. At this time, "video grade" cartridges were readily available for use with video recorders, and these video 8mm tapes were generally about half the price of the data grade tapes. Perhaps surprisingly, some of them were every bit as reliable for data backups as the data grade tapes, especially tapes made by Sony and Fuji. Note, only the low end video grade tapes were suitable for data backups. The "fancy" ones that promised improved video quality often caused problems, both with data recovery and with the drives themselves.
This stands in stark contrast to 4mm data (DDS) and audio (DAT) tapes. DAT tapes would not hold up to the punishment they received in DDS data drives. The tapes tended to stretch after a very small number of uses making them unsuitable as backup media.
In about 1994, Sony changed the formulation of their entry-level video grade tape, making it unsuitable for backups as well. After just a few uses, media write errors would become so prevalent that effective backups were all but impossible. The rumor was that Sony did this to force data oriented customers to pay the additional markup for the data tapes, but to my knowledge this has never been confirmed.
The AME and VXA tapes have to be data grade, and these are very expensive compared to MP tapes. For this reason, Exabyte drives that can handle MP tapes and are available on the used or refurbished market are still very popular among the budget-conscious home user. While the AME and VXA media are much more reliable than the old MP media, the cost differential is still significant.
So, how much does this gear cost? Of course, that's something that's always in flux. Nonetheless, these are prices as listed for drives and media at the time of this writing, and even at a single point in time, prices can fluctuate significantly.
Drives (mostly internal drive prices):
|Drive Model||New Price||Refurbished Price||Used Price|
Media price per tape:
|Media Type||Media Length||New Price|
|AME with SmartClean||225m||$90|
As the reader can see, there is a huge jump in price between the MP and AME/VXA media. The prices for drives themselves seem to rise fairly steadily, although VXA products are generally cheaper than Mammoth products, even for higher storage capacities. Unless one needs to replace drives in an existing jukebox, there's really no reason to be buying Mammoth systems over VXA systems at this point in time. Old systems that accept MP media are still reasonable choices for the truly budget conscious, but reliability can be a serious issue for drives that have already spent many years in service, even if they have been refurbished.
Much more can be said about Exabyte's 8mm tape drives, but I hope this document has served as a reasonable introduction to the list of drives, their histories, and their media. Anyone who has any questions or corrections about the information on this page should feel free to contact me at: firstname.lastname@example.org.
Check out these other good sources of information on 8mm tape drives.