On Mon March 10 2003 14:13, Eric Sproul wrote:
>Hi all,
>I'm familiar with the general theory of how to "rescue" an AMANDA
> tape that's been written with drive compression turned on. 
> Here's my situation:
>
>I've completed my first dumpcycle with my current config, and I'm
>fairly certain that drive compression has been turned off the
> whole time, but I'm not 100% sure.  I now have in place a script
> that ensures drive compression is off, but it was not put in
> place until a number of runs had been done.  I want to make sure
> all the tapes are uncompressed before I reuse them.
>
>My question:  If I do a dd of some amount of data (like dumping
> the first 32K of data as I would if I was saving the label), and
> then see (via mt) that the drive's compression is still off, is
> it safe to conclude that the tape was written with compression
> off?
>
I believe so.  If the drive has a front panel indicator of 
compression use like mine does, I'd use that for the last word.

>I've read posts that indicate a compressed tape will silently set
> drive compression back on, but will that change still be visible
> to mt?

AFAIK, yes.

>BTW, the drive has no DIP switches for setting compression--

That would definitely be unusual...  The lawyers have attacked the 
user stuff in the packaging to the point where it may not be 
mentioned (I mean "Now why would the *user* need to know that?), 
and I'd come a lot closer to being able to believe that as opposed 
to its not having any jumpers or dip switches at all to control its 
powerup defaults.

> it is
>completely controlled by software.  Also, my system is Linux, so
> there are no compression-related device names.  I am relying
> strictly on mt to manipulate the drive outside of AMANDA, so it's
> important that I be able to trust its output.

How are you interpreting the mt report so as to define if 
compression is on or off?  I don't recall seeing that in plain 
english in any mt output report since about RH5.2, and it has 
changed a bit.  Its concise to the point of being obtuse IMO.

-- 
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz  512M
99.24% setiathome rank, not too shabby for a WV hillbilly