It's possible to use a serial port now on your physical host in ESXi 4.1
Few months back, way before the ESXi 4.1 went out I wrote an article about ESXi 4 which was not supporting serial ports. Serial ports are used for locally attached serial devices like a FAX/modems or some UPS devices. This changed in ESXi 4.1 since with this release of VMware Hypervizor now you have the possibility to attach and use the Serial port of the physical host.
The serial port is “seen” in the VM and the VM can use any device plugged into the ESXi 4.1 host. In my case it's a FAX/modem use by one of those VMs. So for me I could move my VM to the host with ESXi 4.1 installed and use my fax software installed in my VM. And I can prepare the migration of my ESX 4.1… to ESXi 4.1
Thus, of course for VMotion it's…. not possible.. A VM configured with serial port can't be VMotioned elsewhere, unless I configure passthrough… ? I'll test…
Also vSphere 4.1 introduces a Serial port concentrator. What is a serial port concentrator? Eric Sloof had already posted an article on Serial port concentrators.
Here is a quick quote from Eric SLOOF's blog….
Administrators use physical serial port concentrators to multiplex connections to several hosts. vSphere 4.1 enables support for virtual serial port concentrators to provide similar functionality for virtual machines. The feature allows you to redirect virtual machine’s serial ports over a standard network link using telnet or ssh. This enables solutions such as third-party virtual serial port concentrators, like the new virtual appliance-based Avocent Cyclades ACS 6000.
Another think, but this is common to VMware upgrades. After the upgrade to the 4.1 version there is the necessity to upgrade your VMware tools, which by the way changes the icon in the taskbar, like in the VMware Workstation 7.1, which I reported too.
All those changes and new features in vSphere 4.1 makes the whole package more attractive for customers.