In case you want have use /globaldevice as separated slice, you should:
1. Create UFS file systems on required device. You require at least 512 MB.
2. Add record for this device to /etc/vfstab
In this case cluster installation script will not create /globaldevice on lofi.
You can use this procedure:
for Migrate the Global-Devices Namespace From a lofi Device to a Dedicated Partition.