In the final session in the product track at cPanel Conference, Nate Custer, QA analyst at cPanel, discussed what web hosts can learn from how cPanel does virtualization.
Custer started off his presentation by assuring the audience that it would not be “another cloud talk”, to which the attendees cheered. He even proposed a game where the attendees could boo if he said the word “cloud.”
Since cPanel does not have a virtualization product to purchase, his presentation went over how cPanel uses virtualization, and his recommendations for web hosts using virtualization or wanting to offer VPS hosting.
Custer says cPanel uses virtualization in three main areas: its testing lab (OnApp, Xen, OpenVZ), developer sandboxes, and its automated tested infrasturcture (libvirt, KVM). Prior to virtualization, test runs used to take 18 hours, he says.
“There’s just no other way to do the scale of testing,” Custer says.
Custer offered some quick stats about virtualization at cPanel. cPanel spins up 60,000 VMs in the past six months, with an average lifetime of about 30 minutes. Its max capacity is about 1300 VMs, Custer says.
cPanel can clone and boot a VM in less than 30 seconds, according to Custer.
Custer was very candid about his recommendations for virtualization. He does not recommend OpenVZ, Xen or OnApp, and went into the various reasons why.
The flaw of OpenVZ is the shared kernel, true live migration and the fact that there is only a five percent performance gain.
“Xen was great,” Custer says. “It was the first open source virtualization.”
But, since then, most of the open source vendors have moved away from Xen to KVM, including Red Hat, Canonical, IBM, and Fujitsu. If you use Xen, you’re building something where most of the experience developers are not working on your product, Custer says.
OnApp is a “really slick software”, according to Custer, but cPanel needed more control.
“We get our sweet startup times because we’re able to control,” Custer says. He also says OnApp has “paper thin margins.”
Custer recommends libvirt which maintains a single hypervisor and is widely used by OpenStack and Eucalyptus for example. It includes full cluster management, and hypervisors auto register and autoprovision storage.
Custer recommends web hosts use multiple small clusters instead of a single large cloud.
Getting your hardware right is critical, he says. Disk design is also important.
Custer says there should be no more than 2 virtual cores for every core. His recommended formula is 20-40 hypervisors, dual NAS and cluster management.
Talk back: What do you use for virtualization? Do you agree with Custer’s recommendations? Let us know in a comment.