can named service requests while reloading?

[Mark.Andrews at nominum.com]

> I am referring to reload time... I thought that named was supposed to
> respond during ZONE TRANFERRS, but ours does not...ALSO I am not sure
> if it is suppose to respond during the time it is reading the zones
> from disk...our does not....  :-( WE have 100,000 + zones.

	Named *does* respond during zone transfers.

	Incoming zone transfers are handled by a seperate process
	asynchronously.

	Outgoing zone transfers use a 64k write buffer and feedback
	from the TCP stack to limit the quantum of resources used
	for outgoing zone transfers.  The TCP high and low water
	marks are set at 32k and 16k repectively.  Unless you have
	a seriously under resourced server (lack of real memory /
	heavy paging) the time to fill this buffers should be
	significantly less than the time to transmit and drain.

	Small zones will often be transmitted as a single write
	operation as the result of being less than 32k.  It would
	be a very unusual configuration however that did not cause
	the write to the TCP socket to fail (EWOULDBLOCK/EAGAIN)
	on larger zones.  I've had to fix enough bugs over the
	years that were a result having to retain state when the
	writes fail and need to be retried later to know that zone
	transfers do pause and allow other quering processing to
	occur.

	We are looking at memory speed vs network speed.  Unless you
	are paging hard memory speed much faster network speed.  If you
	are paging hard memory speed may approximate disk speed.

	Mark
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--
Mark Andrews, Nominum Inc. / Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com