[clug] Can I re-record just the first record of a tape?

[Kim Holburn]

Michael,

Maybe if you write two (small) files first then your archive.  Then write the first file again.  That way even if rewriting the first file overwrites the second file some way the backup which is the third file on the tape should be OK, bearing in mind that a "file" on tape has a minimum size (2Meg?).

Kim

At 7:44 PM +1000 2003/07/28, Eyal Lebedinsky wrote:
>Michael.James at csiro.au wrote:
>> Can I reliably come back and re-record the logfile after,
>>  without messing up the inter-record gap
>>  and zapping the following records?
>
>I am rather sure that you cannot do this. I mean, you can re-record
>a file, but when you close the tape an EOF marker will be written.
>
>Writing the same data to the tape, at the same position, will use
>a different length of tape at different times, based on timing
>(streaming) and natural mechanical variation. So even if the EOF
>(tape mark) was not written, a broken record will likely follow
>the last written one.
>
>Nevertheless, if you leave enough unused space after the log file,
>you may be able to fsf to the next file, skipping the broken
>segment. The software will need to be able to ignore the end
>-of-tape marker (two consecutive tape marks).
>
>And even then it is likely not to work with a modern 'smart'
>tape unit.
>
>--
>Eyal Lebedinsky (eyal at eyal.emu.id.au) <http://samba.org/eyal/>


-- 
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Kim Holburn 
Network Consultant - Telecommunications Engineering
Research School of Information Sciences and Engineering
Australian National University - Ph: +61 2 61258620 M: +61 0417820641
Email: kim.holburn at anu.edu.au  - PGP Public Key on request

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