> On Fri, Mar 28, 2008 at 01:38:43PM -0500, Eugene Vilensky wrote:
> > So there is no such thing as tape skipping?
> 
> I've heard many admins refer to such things without any references.
> I've never seen documentation of it before.  That doesn't mean that it
> doesn't exist.
> 
> Very close to that concept was an older model drive (SDLT or something
> maybe) where it would disable compression if the tape wasn't keeping
> up.  But even that drive wouldn't *skip* tape to keep up.  

At least all the DLT drives have a "capacity mode" and a "performance mode"
with the  following features:

Capacity mode:
- Would always stop the reels when no more data available
- thus always uses the tape to it's full extent

Performance mode:
- Will "fill" with empty data up to a certain amount if no data
in the buffer. Just in case there would be some available later...
- This avoids start/stop of the tape as much as possible
- Will waste a lot of space when the data stream is below the
native speed. My worst case is 40% wasted.

The modes were selectable with a jumper in early DLT drives, but
later this jumper was hard soldered, because of bad 
performance/publicity, using the  capacity mode.

I have been told that the LTO drives have the same functionality
with the exception that they can slow down the reel speed up to
1/4 of the native speed until they start using the perfomance mode.
Have not checked this though so...

Best
Dag

To sign off this list, send email to listserv AT listserv.temple DOT edu and 
type "signoff networker" in the body of the email. Please write to 
networker-request AT listserv.temple DOT edu if you have any problems with this 
list. You can access the archives at 
http://listserv.temple.edu/archives/networker.html or
via RSS at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER