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.
Top Rated Comments
Is it also killing the load monitors elsewhere? We do remote monitoring as the racks are tucked out of sight in a locked room. I rolled the one test bed back to 10.6.7 this morning though, finally had time to do it. Also found one of the Xserve RAIDs had had a minor HD meltdown as well...
If it's just LEDs, then I can live with that.
It really isn't worth rolling back over, there is a simple workaround: -
Kill until reboot: -
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.hwmond.plist
Kill permanently: -
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.hwmond.plist
sudo mv /System/Library/LaunchDaemons/com.apple.hwmond.plist ~/Desktop/
The only thing I have noticed since doing this is the cpu-load leds on the front of our xserves stay fixed where they were the moment hwmond was killed, not a biggie.
HTH
Probably the same way as how they screw all their other business class products (Final Cut Pro, Cinema Displays, glossy Macbook Pros).
My 2007 MacPro(1,1) 4-core runs Mac OS X 10.6.8 client, not server, and was having problems with the Parallels VM (prl_vm) task swamping two cores which was accompanied by the Parallels Desktop v6 app becoming unresponsive. (I did not notice these problems under Mac OS X 10.6.7) Coincidently Parallels Desktop for Mac update US-6.0.12092.670880 was released, which appears to have solved the problem in my case. Perhaps this is related to the XServe issue reported in this thread and an update to Parallels there will help.