I'll answer my own question (as I am now the pre-eminent expert on
this matter): apparently the Exabyte needed a firmware upgrade
(version C224 on this page:
http://www.exabyte.com/support/online/downloads/downloads.cfm?did=1781&prod_id=681).
. No changes to changer.conf were needed.

FL

AMANDA: undermining commercial backup system hegemony one tape drive at a time.

On 10/14/07, FL <lengyel AT gmail DOT com> wrote:
> I'm using AMANDA 2.4.4p3 under CentOS 4.5 on an Itanium. Previously I
> was using a single
> magazine with 11 tapes--there were no problems. After loading a second
> magazine and
> adjusting the config to use 23 tapes instead of 11 (the initial
> magazine has a cleaner tape),
> amcheck Daily fails because mtx -f /dev/sg3 status needs more time.
>
> I've adjusted some delays in changer.conf, but it's not clear which is
> the crucial delay o use,
> and the delays seems to need to be very long (at least 45 seconds).
>
> -bash-3.00$ amcheck Daily
> Amanda Tape Server Host Check
> -----------------------------
> Holding disk /var/lib/amanda/holdingdisk: 61421084 KB disk space
> available, that's plenty
> amcheck-server: slot 4: date 20071006 label Daily04 (active tape)
> amcheck-server: slot 5: date 20071007 label Daily05 (active tape)
> amcheck-server: slot 6: date 20071008 label Daily06 (active tape)
> amcheck-server: fatal slot 7: mtx: Request Sense: Long Report=yes
> ERROR: new tape not found in rack
>       (expecting a new tape)
> NOTE: skipping tape-writable test
> Server check took 422.307 seconds
>
> Amanda Backup Client Hosts Check
> --------------------------------
> Client check: 4 hosts checked in 10.038 seconds, 0 problems found
>
> (brought to you by Amanda 2.4.4p3)
>