Since the release of Mac OS X 10.6.8 last week, a number of Xserve users have reported in Apple's discussion forums (via MacNN) issues with a hardware monitoring daemon known as hwmond generating significant CPU loads of up to 95%.
Member Arminhempel reports a CPU load up to 70 percent after every reboot on several Xserves he manages; Jean-Serge Remy has an Xserve Xeon showing an 84 percent hit, while InfraredAD is experiencing a 95 percent load on a 2008 quad-core Xserve, essentially wiping out an entire core. Both the combo and delta versions of the update have generated errors and, so far, the only reliable way to fix the issue is a downgrade to Mac OS X 10.6.7.
The update also appears to be causing occasional issues with shutdowns and restarts as users attempt to address the hwmond CPU load issue.
Apple has yet to offer a specific solution for the issue, merely walking users who have contacted Apple Support through some troubleshooting steps without a specific resolution in place. But given the volume of complaints appearing in discussion forums, Apple will likely have to release a patch to address the issue.