I recently attended a Newcastle Infrastructure Users Group meeting, which is hosted by Forsythes IT.

The topic for the evening was VMWare and they had a Senior Pre-Sales Engineer from VMWare going through some of the amazing technology, for example. VMotion: The ability to move a virtual machine between two physical hosts while the VM is still running and not miss a beat.

The only problem I noted was it all relied on having at least 2 physical hosts with 32GB RAM each backed onto a SAN. Now if you have been in IT awhile you will notice that a setup as mentioned in my last sentence equals dollars.

However because VMWare supports iSCSI, you could create a relatively inexpensive SAN with GNU/Linux and iSCSI. It shouldn't be too difficult to cobble together several Terrabytes of diskspace out of SATA disks on a 3Ware or similar RAID controller and the aforementioned GNU/Linux and it can become the SAN that the VMWare ESXi servers look at. In fact there are commercial iSCSI products available for example http://www.open-e.com/ which would take the iSCSI configuration out of the realm of art and place it in the domain of a wizard (get it? next next wizard hah hah).

But what can be achieved with the free only VMWare components? You can now download and install the ESXi "Hypervisor" (it's a VERY intelligent shim OS that sits between the physical host and the guest OS's) at no cost.

To see what was possible I used a Dell PowerEdge 1950 with 4GB RAM and 146GB of HDD. The 1st thing to check is that the server you have is on the VMWare Hardware Compatibility List.

After installing and configuring the ESXi Hypervisor I managed to squeeze a copy of Redhat 3.1, CentOS5.2 and Windows XP Pro onto the box without them becoming too sluggish. However if the OS was hosting something hungry i.e. Anything with Java as a component, then you would have to be careful not to overload the box. 3 OS's divided by 4GB RAM doesn't give a huge amount of memory for each VM but it's enough.

In anyones language a 3 to 1, VM guest to Physical host compression is still OK. Think about the 2-4U of space in your rack you can reclaim!

Further to installing the above OS's I managed to plug a Dell Powervault 100T Tape Backup Unit into the Physical Server and then connect it to the Redhat 3.1 guest and perform a restore operation with no problems.

How is the above useful? If you have an ERP or any critical server and want to test your DR procedures in a nice little sandbox environment then the Single Physical host setup with a couple of VM's as above is perfect. You can install it all in it's own isolated VMWare network with no comms to the outside world and away you go. The beauty of the VMWare Infrastructure Client that comes with ESXi is that you can sit at your workstation and perform all your testing from your desk even though the server is miles away.

VMWare has cleverly decided to give away some of it's best technology (ESXi, Server) and subsist on selling the really cool bits that support it. I can't say it's a bad idea. Considering they are now in competition with Microsoft, VirtualBox, XEN, Parrallels and any other number of VM vendors, they need to keep market share and it's a great way to do it.