The diaglog on the configd gets very large very quickly when there are sharding operations going on. There doesn't seem to be a way to turn it off or purge it without restarting the config.

Fri Apr 15 10:44:36 [initandlisten] MongoDB starting : pid=9869 port=27019 dbpath=/home/david/mongodb/config/ 64-bit
Fri Apr 15 10:44:36 [initandlisten] db version v1.8.1, pdfile version 4.5
Fri Apr 15 10:44:36 [initandlisten] git version: a429cd4f535b2499cc4130b06ff7c26f41c00f04
Fri Apr 15 10:44:36 [initandlisten] build sys info: Linux bs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41
Fri Apr 15 10:44:36 [initandlisten] diagLogging = 1
Fri Apr 15 10:44:36 [initandlisten] waiting for connections on port 27019
Fri Apr 15 10:44:36 [websvr] web admin interface listening on port 28019
Fri Apr 15 10:45:36 [DataFileSync] flushing diag log
Fri Apr 15 10:46:36 [DataFileSync] flushing diag log
Fri Apr 15 10:47:36 [DataFileSync] flushing diag log
Fri Apr 15 10:48:36 [DataFileSync] flushing diag log
Fri Apr 15 10:49:36 [DataFileSync] flushing diag log

david@config1 ~: ls -alh mongodb/config/
total 1.4G
drwxrwxr-x 2 david david 4.0K Apr 19 10:44 .
drwxrwxr-x 4 david david 4.0K Apr 19 10:43 ..
rw------ 1 david david 64M Apr 22 10:49 config.0
rw------ 1 david david 128M Sep 28 2010 config.1
rw------ 1 david david 16M Apr 22 10:45 config.ns
rw-rw-r- 1 david david 1.2G Apr 22 10:49 diaglog.4da82194
-rwxrwxr-x 1 david david 5 Apr 15 10:44 mongod.lock