Atlanta-based virtualization pro Mark Dean shares his thoughts in a guest blog for SearchServerVirtualization.com
One of the more popular products in the growing virtualization market is Parallels Virtuozzo Containers. Virtuozzo Containers provide a stable, high performance virtualization platform. However, this same technology also has some drawbacks in restricting the operating systems that can be used for both hosts and VMs.
I deployed Virtuozzo for a customer that wanted to leverage virtualization but was uneasy about the performance of their database server. I suggested Virtuozzo since it straddles the physical-virtual line with OS containers, it is similar to the technology that Sun Solaris uses.
The strengths of Virtuozzo Containers are really in that blurred line between the physical and virtual platforms. Instead of a hypervisor between the OS and the hardware, Virtuozzo Containers virtualize the OS by sharing OS code, files, memory and cache from the root OS, which is called the Hardware Node (and is represented as Container ID 0) in Virtuozzo terms. This means that the VMs are using the hardware directly rather than having calls to the hardware trapped by a hypervisor and then executed which translates into better performance for I/O workloads. This increase in performance is one of the main reasons companies will deploy Virtuozzo. High I/O workloads such as heavy transaction based databases benefit from the shared code nature of the containers.
But as hardware advances with the option of CPU hardware assistance from the CPU manufacturers (AMD-V and Intel-VT), I see Virtuozzo’s technology becoming irrelevant. Since I can now run unmodified VMs using Xen or KVM on Linux and no longer have the (over-exaggerated) performance hit of the binary translation hypervisor (as in ESX), why go with a limiting technology?
Virtuozzo imposes some limitations on what you can run in your farm. Since the VMs are basically sharing code form the root Container OS, you can only run that type of VM on the host. Virtuozzo Containers currently only supports Windows 2003 Server and main Linux distributions. You cannot run Solaris, BSD or NetWare. Now, for some IT shops that may not be a problem but just about all the places I’ve seen, there is a mix of Unix, Windows and for many government places, NetWare.
If a virtualization vendor does not enable live migration, host/VM isolation or embrace the concept of a farm, it is not good for production workloads. Virtuozzo does have some of them, but their isolation is not as good as I like to see. I find that right now only VMware VI3 ESX 3.5 Server has all those concepts down. Xen Enterprise, when coupled with CPU assisted virtualization is the best contender to challenge VMware’s space right now.
Mark Dean is a VMware Professional Partner and a Microsoft Certified Partner with certifications in VMware, Microsoft, Novell, Citrix, IBM and HP along with HP and IBM hardware. Dean has his own virtualization consulting company, VM Computing.