Quoting Craig Sanders (cas@taz.net.au):
nsd would be my next best choice but when i tested it a few years ago, it was still fairly buggy, had more annoying quirks than bind9, and didn't use any less RAM than bind9 (which was my main reason for looking into alternatives at the time - these days, the size of cheaply and commonly available RAM sticks make that mostly irrelevant).
from what i've read, there are good reasons for using nsd if you host many thousands of domains. i host only a handful.
I use it for a very small virtual-machine host that's extremely memory-constrained, and it's been a champ. Memory footprint is _markedly_ better than BIND9's. rick@gruyere:~$ nsd -v NSD version 2.3.7 Written by NLnet Labs. Copyright (C) 2001-2006 NLnet Labs. This is free software. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. rick@gruyere:~$ ps auxw | grep nsd | grep -v grep nsd 32007 0.0 0.0 3536 116 ? S Mar27 0:00 /usr/sbin/nsd -f /var/lib/nsd/nsd.db -P /var/run/nsd.pid -u nsd nsd 32008 0.0 0.0 3928 236 ? S Mar27 0:12 /usr/sbin/nsd -f /var/lib/nsd/nsd.db -P /var/run/nsd.pid -u nsd rick@gruyere:~$ [rick@linuxmafia] ~ $ /usr/sbin/named -v BIND 9.8.1.dfsg.P1 [rick@linuxmafia] ~ $ ps auxw | grep named | grep -v grep bind 18665 0.1 2.5 84872 39004 ? Ssl Mar27 66:19 /usr/sbin/named -4 -u bind [rick@linuxmafia] ~ $ NSD's performance/throughput is also a great deal better, if that matters. The administrative tools and some of the procedures take a little getting used to. I have some notes that I can send if you ever need them.
but overall, i just don't see any compelling reason to switch from bind9 or ISC dhcpd. they meet my needs and don't cause me any problems.
My opinion, yours for a small fee and waiver of reverse-engineering rights: BIND is a slow, RAM-grabbing, overfeatured, monolithic daemon binary. Alteratives are always worth checking out.