On Sat October 24 2009, Leslie Rhorer wrote: > > On Sat, Oct 24, 2009 at 6:52 PM, Leslie Rhorer <lrhorer@xxxxxxxxxxx> > > > > wrote: > > >> I'm going to go on a limb here and say for anyone (with data they want > > >> to preserve), no matter what, backups make sense and are cost > > >> effective. I'm going to be crazy and say that there's no reason that > > >> someone who thinks they can afford a 8TB disk array and dual SLI video > > >> cards, etc, etc, can't also consider some sort of disk or tape backup. > > > > > > I agree with the disk backup, but not the tape. > > > > > >> Cumbersome? Can be. But having worked with datasets and filesystems > > > > > > Cumberesome, slow, kludgy, and expensive. > > > > Well, like anything else, having a system helps. And by system I mean > > a library, barcodes on all tapes, and a good tape storage system. Yes, > > it involves Humans. > > Well, that wasn't quite my point, but it is another aspect of the > issue. > > > >> that run into the hundreds of terabytes, and having backed them up to > > >> tape, it makes sense. If you have something on the order of tens of > > >> disks, sure, go ahead, take that next step and back them up somewhere > > >> else to another set of disks. If you have more disks, seriously > > >> consider tape--in terms of capacity and power consumption (and data > > >> integrity), tape wins. > > > > > > Power consumption, yes. Capacity is a somewhat more complex > > > problem, with a number of variables. For speed, tapes lose > > > > disastrously. > > > > > For cost, hard drives win unless the array is very large. For > > > > reliability > > > > > and availability, drives win hands down. I've had quite a bit of data > > > > lost > > > > > with bad tape sets, and the most persistent problems on my systems > > > which > > > > do > > > > > use tapes involve the tape drives, even sans data loss. Once someone > > > > wiped > > > > > out a directory which someone up in corporate was backing up to tape. > > > > It > > > > > took 3 days to recover the directory, no doubt because no one could > > > find > > > > the > > > > > tape. > > > > I'm not so sure about the speed--you can stream 100MB/sec to a single > > tape drive, and if you have multiple in a library, it just scales > > horizontally. > > First of all, that assumes the tape is loaded and ready. It can > take hours or even days to retrieve a tape and load it. Secondly, while > the tape can stream 100MB/sec, it isn't random access. Finding a 200 byte > file in the middle of a 1T tape backup is going to take a while. Getting > it from an online backup server takes perhaps 10ms after the admin > finishes typing the copy command. Wouldn't you use some 'tar' like format on the tape so there's a file index you can search without having to scan the entire tape? Then you can just "ffwd" (seek) to the position. _should_ be lots faster than reading all of the data from the beginning to the files location trying to find it. Or maybe there's something I'm missing about tapes? > > But, where I was working, we were also duplicating tape sets for > > offsite, which means there was two copies per backup set. > > > > Is this expensive? You betcha! But...you know. The bad old days of DDS > > are also gone, so there's some rejoicing there. > > They may be for you. I have to manage over 300 of the beasts on the > same number of hosts. What's worse, not only are the backups themselves > often incompatible, the drives often can't even use the same tapes. I have > to see to it a half dozen different tape types get stocked in 75 different > cities. Then I have to try to make sure the gopher in every city remembers > to replace the tape. :( > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Thomas Fjellstrom tfjellstrom@xxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
