% ls -l /var/run/[wu]tmp
-rw-rw-r-- 1 root  utmp  364366464 Aug 13 22:00 utmp
-rw-rw-r-- 1 root  utmp  1743665280 Aug 13 22:10 wtmp

That's 350 megs and 1.7 gigs. Cute. Performance sucks for anything needing utmp (w, uptime, top, etc). The 'init' process is spending tons of time chewing through cpu. System %cpu usage says 38% and is holding there on a mostly idle machine.

Lots of these in /var/log/messages:

Aug 13 22:10:27 domU-XX-XX-XX-XX-XX-XX /sbin/mingetty[6843]: tty3: No such file or d
irectory
Aug 13 22:10:27 domU-XX-XX-XX-XX-XX-XX /sbin/mingetty[6844]: tty4: No such file or d
irectory
Aug 13 22:10:27 domU-XX-XX-XX-XX-XX-XX /sbin/mingetty[6845]: tty5: No such file or d
irectory
Aug 13 22:10:27 domU-XX-XX-XX-XX-XX-XX /sbin/mingetty[6846]: tty6: No such file or d
irectory
Aug 13 22:10:32 domU-XX-XX-XX-XX-XX-XX /sbin/mingetty[6847]: tty2: No such file or d
irectory

I'm not sure why /dev/tty1 is the only /dev/ttyN device, but whatever. Either way, mingetty flapping will flood /var/run/[ubw]tmp over the span of weeks and eventually you end up with a system that spends most of its time parsing that file and/or restarting mingetty.

I fixed this by commenting out all tty entries in /etc/inittab and running "init q":

# Run gettys in standard runlevels
#1:2345:respawn:/sbin/mingetty tty1
#2:2345:respawn:/sbin/mingetty tty2
#3:2345:respawn:/sbin/mingetty tty3
#4:2345:respawn:/sbin/mingetty tty4
#5:2345:respawn:/sbin/mingetty tty5
#6:2345:respawn:/sbin/mingetty tty6