Adam Tauno Williams wrote:
Actually that last point is valid. You should never ever actually trust a tape. Buy good tapes, buy good tape drives, keep the tape drive cleaned and don't mistreat the tapes, use bit-level verification** during backus, And despite all that _still_ never actually depend on any single tape. Because the fact is there is no such thing as any mechanical magnetic media that is really dependable, and tape is among the worst, even though there is nothing better.
AFAIR, IBM 3480 and STK 9840 tapes come with a 25-year data retrieval warranty. For longterm storage, I would still advocate keeping two copies, but that would be more to guard against other accidents.
I hear the claim against tape all the time: "tape is among the worst" and I always call "BOGUS!". Tape is an amazingly durable archive media. I've been in charge of a vault full of tapes - failures are very rare and frequently recoverable. People having problems with tape simply haven't been maintaining their archive correctly (cycling out old tapes, maintaining the tape drives, etc...). I've read from tapes that looked like they had been to hell and back - without fail.
I did say there is also nothing really better, and I did not say that I've had "problems" with tapes. 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. Something has to be, no matter hoiw much you spend, something has to be the weakest part compared to the rest. Next comes the fans and then the power supplies usually. Doesn't matter how much you want to spend on higher quality hardware. The highest quality server with the highest quality tape driver and fans, the tape drive or fans are still the first part in that server to go. The other fact is, tapes get kicked around in cars, filled with dust or dirt/sand, exposed to moisture, exposed to heat. Hard drives are bolted inside of the machine and aren't moved or dunked in water and any dirt or dust sits harmlessly on the exterior of the hard drive case not inside where the moving parts and delicate media surfaces are. The data that travels through a network card or that sit in ram doesn't really have any mechanical problems to worry about. Tapes suffer all of this better than most other possibilities, and it's why they are the the best choice in many cases. However they have their points, and then they have their points. You can drop a tape without destroying it, not so much with say a removable hard drive. You can dunk a dvd in sea water for a month without harming it, not so much with a tape! You can read a wad of data off of a backup servers raid array, or write to it, hundreds of thousands of times without degrading or wearing out the media or the drive. With a tape you get _hundreds_ of cycles if you're lucky. That is all I mean by tapes being among the worst forms of data media, yet also there being nothing better. Think of it in terms of the chances of a given bit of data suviving a transfer onto and off of some given media. The most reliable tape system in the universe can't compare with any ordinary hard drive or stick of ram or network card. Those other things handle millions of transactions absolutely bit-level flawlessly, every _day_. If you bought a hundred tapes probably 5 would be bad or go bad withing a few cycles. Of the good remaining good ones, the best one probably couldn't survive anywhere near 500 read/write cycles. 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. And even WITH that human maintenance staff, you still can't claim anywhere near the same level of reliability, because simply that much time hasn't yet passed since the first tape drive was ever invented, to match the number of read/write transactions, even if they were all perfect, which they weren't, to compare with what a cheap ide hard drive does in probably one year. What's better? Depends on your requirements. Every object could be said to be the best possible way to do the exact combination of things that object does. So, that's kind of meaningless. But, for example, If I have a server with live data, and I have a tape drive a and a tape that are known good so-far, and a neighboring server on the network with a raid array and network that are known good so-far. And you tell me: "pick one, write a tape using the backup software of your choice, or copy the data to the neighboring server using the software of your choice, and the if we read back that copy and there is any bit wrong, you will die." I will rsync to the neighboring server without blinking. No contest. But if you have to carry a couple terabytes on a hiking trip through the jungle or the desert or antarctica, without wired or radio transmission. Or place it into a lock box in a vault in a bank, or hide it on your person, then I would choose two copies on tapes over any sort of removable hard drives or current tech optical media. Flash drives are still a question mark to me. I'd take a tape over typical usb thumb drive any day, on the basis of construction quality. But, It's perfectly possible to construct an ssd drive that's embedded in epoxy potting and encased in a sturdy shell that could take far more abuse than any tape, but I don't know how possible it is to protect against static or EM , even with optosolators. Actually given the choice I'd probably do all three. One copy on tape, on copy on blueray, one copy on ssd. They each survive and don't survive different things. If I had to administer a lot of data on a lot of servers scattered around the country in remote colo facilities, and I had enough network connectivity and enough copies of server hardware and enough hard drive space, I'd maintain multiple copies of the data on multiple servers at multiple remote locations from each other with rsync, and employ rolling tar scripts or filesystems that have snapshot capabilities. Providing me with not only multiple copies of data, not only with those copies all being off-site and indeed separate from each other as well, not only with history, but also with ready-to-go, already up & running and configured backup servers to actually run this backup data, and backup network connections to reach them, indeed whole backup hosting facilities ie, power, a/c, etc and, all this without needing any staff to insert and remove tapes nor exotic expensive and rack-space-eating tape libraries. Most colo facilities do offer tape backup as a service so sure, you could pay a service fee and not have to worry about staff, tapes, worn out drives, or rack space, but, my way works equally well in colo facilities or in customer sites or in my own office or indeed basement, and it's all much more immediately available, provides more functionality and flexibility and faster response times and on top of it all, costs less. Tapes have their place, but they are not the last word in data security, disaster prevention, or disaster recovery. -- blw -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org