Server virtualization: Best (and worst) practices (free PDF)
Organizations have been reaping the benefits of server virtualization for a number of years now, but there are still challenges to overcome and pitfalls to watch out for. This ebook taps the knowledge of two virtualization experts, who explain how to effectively deploy and maintain a virtualization environment.
From the ebook:
What are the biggest challenges when virtualizing servers these days?
DB: The biggest challenge in virtualization is still the sharing of resources across your infrastructure and applications. Whichever way you look at it, some things will need to be prioritized over others within the infrastructure.
When designing a virtualized platform it is a balancing act between the competing resources, and most likely you will still have bottlenecks but hopefully moved those bottlenecks to where they have the least impact on your applications. You would need to consider the network provision, both for external WAN traffic as well as storage traffic. If you are consolidating from 100 physical machines each with 1Gb network interface that are fairly heavily utilized down to 10 hypervisor nodes, it is likely you will need to bump the network to at least 10 Gb to cope with the condensed traffic of those systems running on a reduced number of NICs. You can’t always expect to pick the existing network up and drop it into a newly virtualized environment.
Similar issues exist with the storage. Most virtualized deployments still provision a central storage array, and this is quite often the bottleneck for virtualized system deployment. While having a 10 Gb storage network will likely provide you enough raw storage throughput to the array, the raw disk I/O available from the physical disks is often overlooked due to it being less of an issue when applications are spread over a number of physical servers. This means the disks can’t keep up with the number of read/writes being thrown at them from the number of virtual machines, and performance will start to be affected, especially in things like database applications, which rely heavily on disk I/O.