I’m a big fan of what can achieved with commodity hardware for free or little cost using virtualization platforms such as XenServer. Sure, ‘real’ server hardware has benefits. It is optimized to excel in certain disciplines. But ordinary gray box PCs are immensely flexible and for a scientist like me who plays with hardware configurations all the time, they are great. (They also save you money if you have the space for non-rack hardware btw.)
One thing where ‘real’ server hardware shines is remote management. Ordinary PCs typically do not have that. But most of the time they have a feature called Wake-on-LAN. This allows powering them up by sending a specially crafted ‘magic’ packet over the Ethernet. Fortunately, XenServer has built-in support to send those packets within a pool of servers and the Windows GUI XenCenter makes using that feature very convenient.
- To enable Wake-on-LAN for a computer, you first have to enable the feature in the BIOS. It is usually hidden somewhere in the Power Management options. If there is no such option in the BIOS, you might still give it a try: A DELL Studio XPS workstation I tested did not have an option for Wake-on-LAN in the BIOS but supported being powered up like this nevertheless.
- In XenCenter, right-click the server’s name and select Properties. Then choose Wake-on-LAN (WoL) in the Power On tab.
- Make sure the server is up and running, navigate to its Console tab in XenCenter and log in. If eth0 is the interface using which the server is managed and connected to the pool, type in the following two commands:
# /usr/sbin/ethtool -s eth0 wol g # echo "/usr/sbin/ethtool -s eth0 wol g" >> /etc/rc.d/rc.local
- Give it a try: Power down the computer through XenCenter, wait until its gone and then select Power On.