One of the questions I have been answering lately for our clients is, “Do I upgrade to the new version of VMware (vSphere 5) or wait?” This is not always a cut and dry decision for many of us and depends a great deal on your individual situation and aversion to risk. As a refresher, this VMware PDF outlines the different licensing options for vSphere 5, and here is my previous Journey to the Cloud post discussing vSphere 5 upgrades.
First off, I love what VMware has done with vSphere 5. Many great improvements and it is faster and better than 4.1. Auto Deploy will help larger customers deploy new physical hosts quickly and easily and will provide much more efficient patching of ESXi hosts. There are many improvements to storage including Storage DRS (Distributed Resource Scheduler), Storage I/O control for NFS, and support for larger vmdk files. I also think that the Network I/O control for individual VMs will be useful in many environments.
VMware is still selling vSphere 4.1 for a few months so new customers can choose to stay with the tried and tested 4.1 or go right to vSphere 5. The upgrade path from 4.1 to vSphere 5 is not hard and can easily be done with VMware Update Manager so that is not a major concern. Most of the clients I talk to start with 4.1 since it has been well tested, and they do not want any issues on the start of their virtualization journey--especially if they are new to virtualization and do not want to deal with any odd issues that may come up because vSphere 5 is a new version.
Many of our more seasoned clients, who have been virtualized longer, are considering going to the new version. The general consensus, however, is to wait until it has been tested by other users, then upgrade to it after service pack one has been released. The exceptions are customers who need some feature that is in the new software. I have talked to a few customers who are going to vSphere 5 soon to take advantage of Network I/O at the VM level or to support very large files (larger than 2 TB).
The only thing that might give someone pause about immediately upgrading to 5.0 is HA (High Availability). The original HA was based on code that VMware purchased, and they decided to totally rewrite this piece of critical functionality. This is such an important feature that some are preferring to wait and see how it behaves in the wild before trusting it in their critical infrastructure. I do think that everyone (myself included) is being over cautious. vSphere 5 has been out for weeks, and I have not heard of any major issues. The main reason for the caution is that there are many more important workloads running on ESX hosts, thus, any issue with the hypervisor can cause widespread mayhem if something goes wrong.
For the cautious people out there, a good way to ease into vSphere 5 would be to upgrade Tier 2 systems first along with Virtual Center to get a comfort level with the new features and stability. After that, upgrade your Tier 1 hosts once the comfort level has been established.