sporadic timeouts querying bind9

[Klaus Darilion]

Hi!

I use bind 9.9.5.dfsg-3ubuntu0.17 with around 20 slave zones (from small
to huge).

I query the SOA of every configured zone once a second to monitor bind.

Once a day my script reports timeouts (3 seconds) querying a SOA. This
server is a test server, hence it is idle except the monitoring checks.

When inspecting the logs the timeouts are always very close to NOTIFYs
and zone transfers. Are there any known issues that e.g. bind may
suspend queries wile applying the zone transfer? Any other ideas what
could be the reason?

Thanks
Klaus