Preservation of correspondence

Chuck Guzis cclist at sydex.com
Tue Feb 6 11:42:33 CST 2007


On 6 Feb 2007 at 10:38, Jules Richardson wrote:

> > Its verification is practically a non-feature.  Always generate parity 
> > or make redundant copies.
> 
> Yep, that was my thinking too. I really need to find the time to write a Linux 
> util to suck tar data off DLT and checksum file-by-file to test backups; 
> currently I restore the whole archive and then use find/cksum/diff to check 
> against source data, but it's annoying needing that extra disk capacity just 
> for the sake of backup testing.

Back when we were in the data forensics racket, the business of "Does 
a separate verify pass do any good with DLT/DAT/8mm media, 
considering that the recording process is read-write-verify-erase-if-
error-and-retry (this is what you pay the bucks for on these 
drives)"?

We rewound and checked the VTOC at the beginning of the tape because 
doing so would often turn up SCSI data transfer problems, but found 
it unnecessary to provide an automatic separate verify pass.   We did 
provide a manual verification option, however.

Cheers,
Chuck




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