Trying to install ESX 3.X on a new server with greater than 64GB of RAM? Then you’ve probably run into a problem. When looking at the host summary in VC, a host with no VMs on it will appear to be utilizing almost 50% of it’s available RAM! This bug was supposedly fixed via patch, but if you’re running a server that doesn’t have this patch for whatever reason, this might help.
To enable 40 Bit Memory Type Range Registers (MTTR), which is disabled by default, go to the Configuration Tab on your ESX 3.X host. From there navigate to Advanced Settings > VMkernel and find the configuration entry for VMkernel.Boot.force36BitMTRRMask.
Simply uncheck this setting, and reboot your host. When the host comes back online, your RAM usage will be accurate. Again, I believe this bug was fixed in 3.5 U2, but I felt it was important to mention the issue in case folks out there aren’t at U4.
I have tested this fix with several Dell R900 hosts without any issue. If you run into an issue, do the following:
- Boot the host into single user mode
- Edit /etc/vmware/esx.conf
- Add the following line at the end of the file /vmkernel/force36BitMTRRMask = “TRUE”
- Run esxcfg-boot -b
- Reboot the host
