On Thursday 19 February 2009, Dustin J. Mitchell wrote:
>On Thu, Feb 19, 2009 at 2:52 PM, rory_f <amanda-forum AT backupcentral DOT 
>com> 
wrote:
>> how hard would it be to migrate our naming convention over to match our
>> labels ? is there any way of doing it?
>
>Well, the Amanda label is written on each tape, at the beginning -- so
>you'd need to do some tape-drive trickery to rewrite that
>(single-block) file without overwriting the following data.  I'm not
>sure tape drives can do that.
>
>The remaining adjustments in Amanda's metadata would be tricky, but
>not impossible (basically a global search-and-replace over all of
>Amanda's metadata would do the trick).
>
>Dustin

I don't think I'd attempt that unless the drive has a relatively huge filemark 
space.  I tried it years ago with the DDS2 tapes I was using at the time, and 
the discontinuity at the end of that blocks write trashed the rest of the 
tape very reliably.  Because the label is never more that 512 bytes, that is 
all I was writing, with dd, after telling st it was a 512 byte block tape.  I 
could leave it at 512 bytes and make a backup ok, but the speed suffered.  
About the only way I'd attempt it would be to read the whole tape out to a 
buffer, then put the new label data in the 512 byte head of the buffer, 
rewind the tape and rewrite it.

Since head life on a DDS2 is short anyway, I didn't feel like using up half a 
head-wheel (Seagate was VERY unco-operative in supplying me with wheels, 
claiming it was a factory refurbish only job, and which upset me no end since 
I'm fully experienced in replacing DVC-PRO heads which are 1/3rd the size of 
a DDS head) just to get my labels straightened out.  I eventually did, but in 
the course of doing normal backups by rmtapeing the next one in sequence, 
then labeling it correctly before the run.  PIMA.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
What good is it if you talk in flowers, and they think in pastry?
                -- Ashleigh Brilliant