Some enhancements only become truly evident to people when they see them in action. For many features this means something need to go wrong before they kick in. Others are more visible during normal operations. This is the case with the CSV enhancements in Windows Server 2012 R2 Failover Clustering.
One golden nugget here is the CSV placement policy (which really shines in combination with SOFS/Storage Spaces). This will spread ownership of the CSV amongst the cluster nodes to ensure a balanced distribution. In a failover cluster, one node is the “coordinator node” (owner) for a CSV. The coordinator node owns the physical disk resource that is associated with a logical unit (LUN). All I/O operations for the File System on that LUN are are through the coordinator node. In previous versions there is no automatic rebalancing of coordinator node assignment. This means that all LUNs could potentially be owned by the same node. In storage spaces & SOFS scenarios becomes even more important.
It helps all nodes carry their share of the workload as it load balances the disk I/O.
Failovers of CSV owners are potentially quicker and more predictable/consistent as an even distribution ensures that no one node owns a disproportionate number of CSVs.
When losing storage access the number of CSVs that are in redirected mode is potentially less as they are evenly distributed. In an unbalanced cluster it could be for all of them in a worse case scenario.
When using SOFS with Storage Spaces it makes sure the Storage Spaces Ownership is distributed fairly.
When does it happen
Each time a node leaves or joins the cluster. This means you don’t need to intervene manually or via PowerShell to get an even distribution. This goes for both exiting nodes as when adding a new node. The new node will get a CSV assigned if there is any on surplus on one of the existing nodes.
The process also works when you start a failover cluster when it has shut down.
When customers see this in action (it’s most obvious when then add a node as then they are normally watching) they generally smile as the cluster does it job getting the best possible results out of their hardware.
With November 2012 Patch Tuesday having come and gone, the first hotfixes (it’s a cumulative update) related to Windows Server 2012 are available. These are relevant to both Hyper-V & Failover clustering (Scale Out File Server) There is also an older hotfix that has been brought to our attention that related to certain versions Windows Server 2008/R2 domain controllers,which is also important for Windows Server 2012 Clustering. None of these are urgent/critical and only apply in specific circumstances but it’s good to keep up with these and protect your environment..
Windows 8 and Windows Server 2012 cumulative update: November 2012
http://support.microsoft.com/kb/2770917: A collection of small changes – for HA VMs (Hyper-V on Cluster) there are three minor CSV file system fixes in this Hotfix : Improves clustered server performance and reliability in Hyper-V and Scale-Out File Server scenarios. Improves SMB service and client reliability under certain stress conditions.
Error code when the kpasswd protocol fails after you perform an authoritative restore: “KDC_ERROR_S_PRINCIPAL_UNKNOWN”
http://support.microsoft.com/kb/976424: Install on every domain controller running Windows Server 2008 Service Pack 2 or Windows Server 2008 R2 in order to add a Windows Server 2012 failover cluster. This is included in Windows Server 2008 R2 Service Pack 1. So just see if you need this fix in your environment or not.
I’m happy to see Microsoft acting fast on these issues,, even if not critical, to serve & protect their customers deployments.
I know a lot of you are, just like me, actively investigating Windows 8 & Hyper-V. You’re downloading the Beta, reading blog post, discussing scenarios and use cases and that’s great. You’re investing in a bright future
Here are some blog post that contain gems of information and that I’d like to bring to your attention:
I already mentioned that during the Experts2Experts Virtualization Conference I met a lot of great people and I presented on High Performance & High Availability networking for Hyper-V clusters (10Gbps goodness). Some of the people I met I already knew from the on line community and others were unknown to me until that event. Among the attendees we found some of the usual virtualization suspects in our community like Aidan Finn, Jeff Wouters, Carsten Rachfahl, Ronnie Isherwood.
Now Carsten Rachfahl is a MVP in Virtual Machine expertise but he’s also a dynamic entrepreneur who shows a lot of initiative. Using social media he is really making in effort to get people & customers to notice important snippets of information by providing easy and fast access to them. He’s very active as a speaker, on Twitter and on his blogs. On top of that he does podcasts and video interviews. For Hyper-V information go to http://www.hyper-v-server.de/ which you can also use as an entry point for his other sites focusing on several aspects of IT in the Microsoft sphere in Germany. Like cloud computing & Licensing. There you’ll also find the videos of interviews on these subjects. It’s quite an impressive endeavor.
Carsten took the opportunity to make some videos with all the above suspects on various subject and he recently released our interview.
In this video we continued the discussion that Aidan started on CSV and we briefly touched on a subject you could make hour long documentaries about: storage options in Windows Hyper-V now and in the years to come. Enjoy!
As I’m building or extending a number of Hyper-V Clusters in the next 4 months I’m gathering/updating my list with the Windows 2008 R2 SP1 hotfixes relating to Hyper-V and Failover Clustering. Microsoft has once published KB2545685: Recommended hotfixes and updates for Windows Server 2008 R2 SP1 Failover Clusters but that list is not kept up to date, the two hotfixes mentioned are in the list below. I also intend to update my list for Windows Server 2008 SP2 and Windows 2008 R2 RTM. As I will run into to these and it’s nice to have a quick reference list.
I’ll include my current list below. Some of these fixes are purely related to Hyper-V, some to a combination of hyper-V and clusters, some only to clustering and some to Windows in general. But they are all ones that will bite you when running Hyper-V (in a failover cluster or stand alone). Now for the fun part with some hotfixes I’ll address in this blog post. Confusion Take a look at the purple text and the green text hotfixes and the discussion below. Are there any others like this I don’t know about?
When you try to install the hotfix it will. So is it really in there? Compare file versions! Well the version after installing the hotfix on a W2K8R2 SP1 Hyper-V server the version of vmms.exe was 6.1.7601.21642 and on a Hyper-V server with SP1 its was 6.1.7061.17514. Buy the way these are English versions of the OS, no language packs installed.
With hotfix installed on SP1
Without hotfix installed on SP1
To make matters even more confusing while the Dutch KB article states it applies to both W2K8R2 RTM and W2K8R2SP1 but the English version of the article has been modified and only mentions W2K8R2 RTM anymore.