Per Jessen wrote:
Brian K. White wrote:
I have had to deal with bad tapes and bad drives but it's a simple fact of life that the tape drive is the first thing to go in just about every standalone back room server. The dust kills it , and if not that then the simple fact of it being the most moving-part. Even when the on-site people are really good about actually using the cleaning tape. Even when the particular site isn't all that dusty. It's simply by far the weakest, most delicate and easily broke and first to wear out piece of equipment in the server.
I agree with all of the above, but a server sat in a broom cupboard somewhere doesn't quite fit in my operating strategy :-)
Reading the rest of your posting, I think we are looking at two different ends of the scale wrt tape usage. Like others, I have spent quite a few years of my professional life working with tape. Most recently a few years at StorageTek writing system software for tape libraries/robots.
The most reliable tape system in the universe can't compare with any ordinary hard drive or stick of ram or network card.
Quite the contrary. The most reliable tape system in the universe will easily outlast any ordinary hard drive. Even the r/w head of an STK drive has a guaranteed lifetime of 8.5 years. An ordinary harddrive will die after five years, on average.
If you want to take the concept of a tape system as a whole, including the process of cycling out old tapes and old tape drives, well, gee, that only works by dint of a human manuall, actively replacing parts continuously, being knowledgeable and always doing the right thing. That's kind of a ridiculous amount of overhead compared to a hard drive that can read and write a zillion times perfectly all by itself for free for some number of years.
You might be right, but when we're talking about tape, it's because we're talking about reliable storage, not read/write operations.
Brian, take any ordinary harddrive today and write a file to it. I'll do the same to a 9840 tape. Then we store them in a dry place at 10-20C for 10 years. I'll bet I can still retrieve the file, and I'll also bet that you can't. (I've already tried both).
/Per
How many write-read cycles does the best tape in the world accomplish before it fails? How many write-read cycles does even an ordinary hard drive accomplish before it fails? That is what I mean. It is simply one metric among many. The fact that a tape may be better by some other metric doesn't change this one. The chances of any given write and then read operation completing successfully are astronomically higher for any of the fast things like ram and hard drives, than any of the slow things like tape, simply because the hard drive actually has been proven by writing and reading a million transactions. No tape can claim that. You write to a tape infinitesimally fewer times. Even if the success rate is 100%, the sample size is still so ridiculously smaller that you can not call a tape which successfully writes/reads 300 times in it's entire life time, anywhere near as reliable as a device which successfully writes/reads 300 times _per second_, for years. You are presenting an entirely different, also valid metric. A very good tape probably has a greater chance of reading without any errors after sitting around for 20 years than a hard drive. Greater but still nowhere near great. Even 99% chance is not great at all compared to what a hard drive does every second. And really, who knows, maybe that tape and the hard drive have exactly the same chance after sitting around 20 years. Any hard drives that are currently 20 years old are nothing like the ones today, and why should a hard drive degrade any more in 20 years sitting unpowered on a climate controlled shelf than a tape and tape drive? What? I shouldn't count the drive? In 20 years they will be manufacturing and selling new LTO or any other drives that can read any of the current types of tapes? Even backwards compatibility has not gone that far so far so I don't know how you can bank on that happening more in the future. Where is the current tape drive made today that can read any tape that was made 20 years ago? Even exotic high end situations where its not unreasonable to have such drive custom manufactured just for you, doesn't always get what it needs in time to save the data. What about all that priceless NASA sattelite and remote probe research data thats disintegrating _as we speak_ on tapes? I said essentially "don't trust a tape" Someone attempted to counter that with essentially "that's bogus, the entire process of using tapes is perfectly reliable" The second statement has no bearing at all on the first and in no way contradicts it. In fact the process of using tapes has at it's core the very precept of trusting any individual tape as little as possible. You make many copies, you read each copy back as soon as you write it, you aggressively cycle out tapes while they are still practically brand new in that they've only been used a handful of times (50 to 200). Those are not policies that reflect a high trust in the base media. You don't buy a new hard drive every 200 writes, or even every 200 days with countless writes per day. You could also say that monks hand transcribing manuscripts on vellum by candle light are more reliable than tape or hard drives or anything else, and no one can prove otherwise. Because monks and cross-verified manuscripts have already existed for thousands of years and tapes have not. Fate accomplis. But of course the human and the vellum are not reliable. Only the entire process of many humans checking each others work, and many copies of the data to compare against each other, is reliable. -- bkw -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org