IXFR journal dump making 9.2.4 server non-responsive

[Derek D.]

We subscribe to an e-mail DNS RBL that we zone transfer via IXFR and
have noticed what we believe to be a correlation of BIND stop answering
queries and the dumping of the journal file to disk.

The server is a Sun v120 with 2GB of RAM running Solaris 8 and Bind
9.2.4.

I noticed the Bind 9 ARM mentions that the default time for dumping the
journal file to disk is 15 minutes, but we seem to be seeing it at
about 20 minutes.  For example the end of transfer log entry for the
zone is at 00:56:25 and all is well until 01:16:51 when log entries
stopped.  Then at 01:20:45 queries start getting logged again.  During
this outage the machine is running pretty close to 100% CPU and a truss
shows that a new zone file is being dumped to disk.  Normally the
machine is running with a load average of about 0.2.  A fresh start of
BIND takes about 8 to 10 minutes to load this zone plus the others that
is has.  The RBL zone file is about 102MB.

Does the above make any sense?
Would a dual CPU box help this?
Any ideas or suggestions?

Thanks,
Derek D.