[Info-vax] strange backup behavior

[Bob Koehler]

In article <e7dbbd3a-17e4-469c-b2e3-4a450c788d0b at p36g2000prn.googlegroups.com>, B Hobbs <bdhobbs18 at acm.org> writes:
> I've noticed that the more data on our backup SDLT tape, the longer it
> takes to add additional files to the same tape.  When a file of about
> 35 blocks (BACKUP-STUFF.COM;67) is backed up at the beginning of the
> tape, that backup takes less than a minute.  Backing up the same file
> after about 45 gigabytes of other backup files takes over 30 minutes.

   Every time you moiunt/dismonut a tape, it rewinds, even if you don't
   unload it.  When you add a save set to the end of a tape, BACKUP
   has to search forward for the logical end of volume marker (two
   EOF markers together).

   Some tape drives have the search for EOF capability in thier own
   firmware, for others the driver has to read each block until it
   gets an EOF.

   What model SDLT?  Probably someone knows how it works.