Hi Jon,

> 
> 1. you are writing to a dds2 tape, 3.8GB max size, and /dev/sdc2 is more
> than 4 GB, even compressed.

it's a dds4 tape, you know, 20Gb and 40Gb compressed. My backups aren't greater 
than 6Gb totally ( when full dump ). these indications aren't normal , the tape 
must to have more than 3.8 Gb
> 
> 2. you have no holding disk available for /dev/sdc2 so it is writing
> directly to tape.  for some reason this is too slow and some timeout
> is kicking in.

I add below notifications from my Debian ( log check). You can see many strange 
errors, specially  "Jun 24 03:06:06 xaloc kernel: st0: Error on write 
filemark." repeatedly.

I don't understand what happens ...

> 
> 3. you have holding disk space available but have not set a chunk size
> below the maximum file size limit of your holding disk.


--- LOG CHECK ---


Unusual System Events
=-=-=-=-=-=-=-=-=-=-=
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc kernel: st0: Error on write filemark.
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc sendbackup[20682]: index tee cannot write [Broken pipe]
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc kernel: st0: Error with sense data: Current st09:00: 
sense key Medium Error
Jun 24 03:06:06 xaloc kernel: Additional sense indicates Excessive write errors
Jun 24 03:06:06 xaloc kernel: st0: Error on write filemark.