Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!ingr!b11!mcconnel From: mcconnel@b11.ingr.com (Guy McConnell) Newsgroups: comp.periphs.scsi Subject: Re: DAT versus 8mm Tape Message-ID: <9350@b11.ingr.com> Date: 8 Nov 90 19:43:28 GMT References: <272DB1E1.9737@orion.oac.uci.edu> <27388281.13536@orion.oac.uci.edu> Organization: Intergraph Corp. Huntsville, AL Lines: 118 In article <27388281.13536@orion.oac.uci.edu>, sfrank@orion.oac.uci.edu (Steven Frank) writes: > Several people requested a summary of the 8mm versus Tape debate: > > 1. All 8mm units are currently made by Exabyte, although other > manufacturers package the drive. The current model that is > available is the EXB8200, which holds 2.3 GB per tape. Each > tape costs about $7. This model is available from anDATAco > for $2400. Call (800) 334-9191. Kubota of Japan also manufactures these drives and sells them in the Pacific Rim. All U.S. destined units made at Kubota still go through the Exabyte facility in Boulder for read/write compatibility testing, quality control, etc. The current product spec states that the drive (with the 112m Exatape) will hold 2.5 Gb per tape. I can easily get 2.1 to 2.3 Gb per tape EVERY time, now matter what you have been told. > 2. The 8mm EXB8200 has a very slow seek time. A new model available > next month, EXB8200-SX will have a seek time comparable to DATs > (so they say). The new drive has a chip that counts servo pulses. > How well it works in practice is not known (eg, drivers, etc). > The new model is about $3000. Finally, a EXB8500 will be out > soon that has fast seek and holds 5 GB per tape. The EXB-8500 has a faster seek time than DAT. > 3. People using the Exabytes are uniformly pleased with performance, etc, > but of course do not use the machines for anything other than dumps > since the seek times are slow. Also, the drives apparently need > to be cleaned about every 30 hours of use, and cleaning does > affect performance. I am very pleased with the Exabyte drive and I use it for backups, restore operations, data exchange, etc. The drives do need cleaning every 30 Gb or monthly, whichever comes first. The cleaning cartridge will not cause head wear and therefore will not affect performance. Not cleaning the heads will degrade performance on the Exabyte as well as any other tape drive (including DAT!). > 6. Some advantages claimed for DATs relative to 8mm: (a) DAT is digital > whereas 8mm is an analogue medium (why this is a big advantage isn't > clear, beyond obvious fact that data from hard disks are digital); > (b) DATs are cheaper; (c) DATs are self-cleaning; (d) DATs are the > tape drive of the future, so prices will continue to drop; (e) fast > seek is easier to implement for DATs because of the mechanics of > read/write and storage; (f) DATs have enthusiasm of many vendors. > (g) future DATs will have higher capacities than 8mm.. > > 7. My current impression of the claimed advantages in 6: > (a) I don't know??? Ask someone from the DAT camp to attach a scope or analyzer to the output of the head and show you the "digital" signal. What? It's analog too? Well, imagine that. All magnetic recordings are analog, including hard disks. > (c) Seems to be true Someone is pulling your chain. They are NOT self-cleaning. There are DAT cleaning cartridges to use for this purpose. They look just like regular DAT tape because they are an abrasive chromium dioxide formulation, just like consumer 8mm video cleaning cartridges. Go to the video store and read the fine print on the cleaning cartridge. It says "Do not use cleaning cartridge excessively as premature head wear will result". That is why Exabyte uses a specially developed cloth cleaning cartridge and use of a video cleaning cartridge will void their warranty. > (d) Hard to judge. Many manufacturers are selling or developing > DATs. Apparently they can and will soon be made in 3.5" form > factor, and will be pushed in the PC and MAC market. Acceptance > in these markets guarantees lower prices, more competition > and more variation in product quality, with the best being > very good. There is currently one manufacturer shipping 3.5" DAT drives (I have one in my lab). There is a shakeout going on in the DAT market after which only the "major players" will be left. > (e) Appears to be true, although new Exabytes are said to be just > as fast although more expensive. Fast search is just as difficult to implement on one as the other from a software standpoint. > (f) True > (g) HP has announced a 2 GB 3.5" DAT (35470) and a similar drive > with hardware compression (8 GB with compression). 8mm is > near releasing 5 GB drives. My guess is that DATs may be > behind here, but price per GB may soon favor DATs. (The new > HP drives will not be available for 6 to 9 months). Most or all of the DAT vendors are working on a 3.5" drive. Only one is shipping them now but it isn't HP. Bear in mind that the same type of media is used in both 8mm and 4mm and that anything that can be done to increase capacity on DAT (i.e. compression and longer tape) can be done on 8mm as well. The converse is not true. DAT is close to maximum areal density with current technology at 114 Mb/sq. in. and therefore cannot easily (possibly?) increase capacities by increasing track density. Current 8mm tape is at 35 Mb/sq. in. and the new 5 Gb drive will have and areal density of 74.4 Mb/sq.in. This gives a path to double capacity once more after this WITHOUT data dependent compression algorithms. > 8. Overall, it is a toss-up at present. The future does seem to favor > DATs, but that is hard to predict. Both have their strong points but, until quite recently, all of DAT's claims and selling points were on paper only and not field proven. They are only now begining to ship in sufficient volumes to verify or nullify their specs. Stay tuned. -- ============================================================================ Guy D. McConnell | | "I'd like to be Intergraph Corp. Huntsville, AL. | Opinions expressed | under the sea Mass Storage Peripheral Evaluation | are mine and do not | In an octopus' Tape Products | necessarily reflect | garden in the uunet!ingr!b11!mspe5!guy | Intergraph's. | shade..." (205)730-6289 FAX (205)730-6011 | | --The Beatles-- ============================================================================