Preservation of correspondence
julesrichardsonuk at yahoo.co.uk
Mon Feb 5 19:13:03 CST 2007
Jim Leonard wrote:
> Al Kossow wrote:
>> >> Is everything you're 'backing up' checksummed?
>> > Yes. I regularly ( == when I remember!) backup my email
>> > by throwing it all into a zip archive and then that gets
>> > written (along with other stuff) to CD, along with an
>> > MD5SUM file.
>> Good for you!
> Yes, but the md5sum will only detect corruption, not correct it.
I've always used DLT for backups in recent years; far as I'm aware they have a
reasonable level of error detection / correction information built in at the
lowest level, I don't see them dying out for a long time, and I prefer the
fact that the media's self-contained (unlike CD / DVD which runs the risk of
attracting dirt / fingerprints due to handling).
I tend to keep two copies of any data on separate tapes (uncompressed tar
format) plus a third copy on a hard disk (which only gets plugged into a
system for the duration of a backup run).
Test restores are always done, using the cksum util on each restored file for
comparison  against the original data just to verify tape integrity.
 Yes, tar has some verification options built in, but at least for the GNU
version the documentation seems to be a bit lacking; I'd trust cksum's output
more for detecting any problem files as it's not entirely clear what exactly
tar does for the verify step.
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