> 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. > 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
