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In the previous posts for this series, I discussed why we decided to upgrade our virtual machine host servers from Windows Server 2008 to revision 2. I also outlined the implementation plan.
Now that I’ve gone through the actual upgrade, I want to share how it went.
Cluster Shared Volumes
While there may not be any performance or high availability gains from this feature, I consider it a great one from an administrative standpoint.
To illustrate my point, consider the number of disks needed to have clustered Exchange 2007 servers running as VMs in revision 1. For each server one disk for Windows, a disk for each database, and a disk for each set of transaction logs is needed. With just one mailbox store, six iSCSI disks are needed. When you add in the disks you need to run Hub Transport and Client Access servers you easily need 8-10 disks just for email.
Hyper-V Upgrade - Cluster Shared Volumes
Throw in the other disks you need for redundant domain controllers, remote access servers, and SharePoint, and they begin to add up. Compare this with cluster shared volumes where the only “disk” is accessed using C:\ClusterStorage. Now one disk is provided and vhds are maintained. If a server requires more space than anticipated, simply expand the vhd. This is much easier than taking the iSCSI target offline, extend that image, and then expand the vhd.
An additional bonus in VM disk management in R2 is the ability to add virtual hard disks while the VM is still online. No more shutting down Exchange to add another drive for that new database you need to create.
I mentioned in previous posts that I wanted to take advantage of all that memory sitting in my hosts and still allow all VMs to failover to one host in disaster scenarios. Dynamic Memory solved that problem. We no longer have 50% of our RAM sitting around unused when the hosts are under normal conditions.
To accomplish this we simply kept the total startup RAM assigned below the total available RAM on one host. Attention was also paid to the memory buffer percentage so that even with the additional RAM that setting allocates, we still sat below the total available RAM. The maximum RAM setting allowed us to provide additional RAM capacity when unused RAM is available.
Hyper-V - Dynamic Memory
Finally, using the Memory weight setting allowed us to prioritize important VMs such as an Exchange mailbox server over less important VMs such as a redundant domain controller. Dynamic Memory is also very easy to configure.
Being conservative from a budget standpoint, we’ve been looking forward to having Live Migration without the need for additional expense of System Center Virtual Machine Manager (SCVMM).
Hyper-V - Live Migration
I’m happy to report that the feature has worked well so far. There’s really not much else to say about this feature. It lets us move VMs around without having them lose connectivity which means we can do maintenance during working hours.
In summary, we’ve been very happy with the improvements that R2 brings to the table. The key features that moved us to upgrade perform as advertised.