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Dividing the Linux desktop
LWN.net Weekly Edition for June 13, 2013
A report from pgCon 2013
Little things that matter in language design
there's nothing inherently wrong with using hard drives or optical media for backups.
the key is having copies offsite and testing them so you know you can use them
Obnam 1.0 released
Posted Jun 13, 2012 21:52 UTC (Wed) by Baylink (subscriber, #755)
But, no, my research and my experience both concur: there are in fact /inherent/ problems for using spinning magnetic or optical storage media rather than tape, for archival storage in the category which most people expect when they say 'backup' - and they're order of magnitude differences.
If you have a backup on disk or CDr from 1992 that you can still read reliably, I'd be happy to hear about it.
Posted Jun 13, 2012 22:02 UTC (Wed) by dlang (✭ supporter ✭, #313)
if you are doing long-term archiving, no single copy is a valid long-term storage. In every case you need to have multiple copies, with error correction, and test them frequently enough so that when one copy fails to read you can still get the data from one of the other copies.
you should be migrating your data from one generation of backup to another on a frequent basis if you are doing long-term archiving.
However, most people are not talking about long-term archiving when they talk about backups, they are talking about disaster recovery, getting the systems running again with the data that is online and available just before the disaster. For that you need multiple copies, and geographic distribution of the copies, but you don't need to read media that's been in storage for 20 years.
Posted Jun 15, 2012 3:08 UTC (Fri) by Baylink (subscriber, #755)
In short: yes: tape drive hardware design engineers are nearly fetishistic about backwards compatibility, drive longevity, and interchange.
And you're correct in saying that it's generally not a *requirement* to read data that old -- but the fact that you can usually contributes to making it easier to read data that's much newer.
One other reason, BTW, that that was possible?
Non-proprietary *backup software*; those tapes were written with a "super-Tar" program, Microlite's BackupEdge, I think, so that even if that
software was either no longer available or incompatible, I wouldn't care: *tar* could read the tapes.
You're certainly correct, though, in noting that for "true" archival storage, it's a job in itself, migrating to newer formats and layouts. This would be a vote in Obnam's favor; at least you could keep the package around in source, and as long as you could make it build, you could retrieve stuff.
I have in fact had to retrieve 5 year old backups, of accounting year-ends when a merger was being contemplated. That was when my client turned out to be really happy about all that money they'd had to "waste" on backup tape (nightly full, 5 Friday's, 3 EOM, 4 EOQ, pre-close and post-close).
Posted Jun 19, 2012 12:42 UTC (Tue) by ekj (guest, #1524)
I could keep a dozen 20MB hdds around, or I could store their entire content as a tarball on a single current disc, and have them take up 240MB, or 0.012% of the capacity of one disc.
Then I could add in a half-dozen 500MB hdds from a few years later, a few 10GB discs from a few years later, and 2 or 3 100GB-discs from a few years ago. This adds up to dozens of discs.
Or I could do the sane thing and store all of these as files on a current disc. In sum total they take up about 10% of the storage-capacity of a single disc. And they're instantly accessible if I actually want to use any of the old files.
For security, I have a second copy on a disc in my basement, and a tertiary copy in an online account on a different continent that costs less for a year than the electricity for the old discs would cost.
Why try desperately to keep old storage-media alive when it's not the media but the *data* that has value, and that data is by nessecity trivial in size today ?
Barring exceptional circumstances, *nobody* have digital data from 1993 that aren't trivial in size.
Posted Jun 14, 2012 1:21 UTC (Thu) by bronson (subscriber, #4806)
Yes, I have a 1996-era backup on disk. It's an 80MB tarfile sitting on my 1TB stata hard disk. Of course, it's not the SAME disk. So what? Next time I upgrade disk drives, I'll just copy it over with everything else. Works great.
(Not much of value in there, just some Mac System 7 utilities I wrote and an old mail spool. Utterly worthless. I'd delete it if 80 MB weren't completely inconsequential these days...)
CDr, you're absolutely right. Not a chance. Those start dropping bits after 6 months.
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