I don't know if 2.5.1 is old enough to qualify for this issue, but it used to 
be the case that the entire set of disklists for a client had to fit in a 
single packet. What that meant is that if you had more than a few dozen disks 
on one client (depending on disklist options), you would run into this issue.

The solution is to upgrade, but a workaround is to create a second IP address 
and DNS name on the same physical client, and move some of the disklist 
entries to the latter.

--Ian

On Wednesday 05 November 2008 13:57:22 Dustin J. Mitchell wrote:
> On Fri, Oct 31, 2008 at 9:01 AM, Leon Meßner
>
> <l.messner AT physik.tu-berlin DOT de> wrote:
> > i get the following message with Amanda-2.5.1p3 on FreeBSD7.0:
> >
> >        FAILED [hmm, disk was stranded on waitq]
> >
> > planner: ERROR Request to myhostandserver failed: error sending REQ:
> > send REQ to myhostandserver failed: Message too long
>
> As you've no doubt discovered, this means that the REQ packet was too
> large to fit into a single UDP datagram.  I know that we've added some
> additional information to the packets in recent versions, but I don't
> know why that would be the case in 2.5.1.  Have others seen a similar
> error?
>
> Dustin
-- 
Zmanda: Byte & Switch "Top 10 Storage Startups", July 2008