So, as many of you know, I manage a virtual datacenter. Good times, high stress, fun challenges.
Today, I was able to cut out almost 5% of my CPU usage by virtualizing a network switch with Open vSwitch. Now that all inter-VM communication is done through kernel modules, the physical network hardware is used significantly less – which means the CPU doesn’t have as much to deal with. I’m still testing the waters to see if this major adjustment is worth it. If the saved CPU turns out to be worth less than the network performance, I may go back to standard linux bridging.
To give you a brief glimpse of my physical environment, I’m serving the data through an iSCSI target with 16GB RAM and an Intel quad-core i7-2635QM CPU at 2.0GHz. The virtual server is beefier, with 64GB of RAM and dual hexa-core Intel Xeon E5-2630L CPUs at 2.0GHz. (The energy-efficient L-series processors are absolutely wonderful!) The un-routable and private subnet that makes up the iSCSI “data bus” is built with one Intel I340-T4 on the iSCSI target and an Intel I350-T4 on the VM server, with up to 4Gbps of bandwidth. I have yet to see the maximum bandwidth usage pass 1.2Gbps at any given moment. Since I’m desperately in need of some more physical NICs for the virtual machines, I may choose to drop a couple linux out of the bond … But we’ll see how it goes.
At this time, I am hosting 11 virtual servers on one box. Six as Windows 2008 R2, and five Ubuntu-based linux servers. Performance is wonderful, mainly due to the RAID1+0 array of solid-state drives. Data storage/access has yet to show any signs of bottlenecks, though quite a bit of memory is dedicated on the VM host for caching. Again, we’ll see how it goes. I’m monitoring things pretty closely these days with Cacti, and any necessary adjustments are done on the weekends. (So much for having the weekends off …)
A simple note for those of you that try this running Ubuntu 13.04 Raring Ringtail … Make sure to install openvswitch-datapath-dkms instead of the commonly referred-to package openvswitch-datapath-source. You won’t get very far with the “source” package. It requires kernel headers for a different version, so anything 3.8.x confuses it.