Preservation of correspondence

Jules Richardson 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 [1] against the original data just to verify tape integrity.

[1] 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.

cheers

Jules



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