Clarifying How Virsto Plays with Hyper-V R2 Cluster Shared Volumes
Posted Monday, August 22, 2011 in Technology 0 comments
On Hyper-V, a good number of our customers are using failover clustering. A few questions have been surfacing about how Virsto can best be used in a failover cluster environment, so I thought I’d make a few comments about that.
First, let me state that Virsto vDisks co-exist with CSVs in every Windows Server Failover Cluster environment we have in our customer base. A CSV is a volume that is available to directly read from and write to by all nodes in a failover cluster, and it’s the best place to put the VM configuration data in a failover cluster. Virsto’s user manuals actually recommend that customers configure a CSV for this data in every Virsto Server Pool that is also a failover cluster. So if you’re using Microsoft failover clusters with Virsto, you will have at least one CSV in every configuration.
Where we recommend that Virsto vDisks be used in a failover cluster is for the VM image and user data. This is where some of Virsto’s unique features have real value – the ability to place this data on very high performance, thin provisioned Virsto vDisks that support very scalable snapshot/clone technology makes Hyper-V perform even better during runtime operations as well as during VSS/DPM backups (which by the way, Virsto fully supports). Virsto supports very granular operations at the VM level – not the LUN level – even though its running on top of block-based storage. That means you get the flexibility you need to Live Migrate individual VMs where you want them without having to worry about how you’ve laid out your underlying LUNs.
By the way, Virsto just received Windows Server 2008 Certification, just to underline our ability to fit into Hyper-V environments. If the logo is not up on our website yet, it should be up shortly.
Let’s just make sure everyone knows what a vDisk is. Virsto CTO Alex Miroshnichenko has already covered the detailed implementation of vDisks in a Hyper-V environment, but it wouldn’t hurt to review that again. A Virsto vDisk looks to Hyper-V exactly like a Hyper-V fixed VHD, but it is thin provisioned and runs at the same performance as a pass through disk regardless of whether it has any snapshots or clones attached to it. To understand why this is true, you can read up on our virtual storage architecture on our website. This Virsto “virtual VHD” is only a namespace object - just an entry in a virtual directory. The Virsto filter driver, which is what you install in the parent partition of each Hyper-V Host, maintains the linkage between a Virsto VHD namespace object and the corresponding vDisk that contains the actual data. By attaching or mounting a vDisk to a Hyper-V VM, this linkage is established. Once that’s done, all the I/O requests flow directly between the VMs and the appropriate vDisk.
To sum up, it’s the combination of Hyper-V, failover clusters, CSVs, and Virsto vDisks that together create a compelling hypervisor platform for either virtual server or virtual desktop deployments that trounces the hypervisor competition. Virsto enhances this Hyper-V configuration so that, with a given storage configuration, it will support a virtual machine density that is at least 2x higher than native ESX while it at the same time outperforms it on an IOPS/spindle basis. And it provisions faster, using our scalable snapshot/clone technology, than a high end, enterprise-class storage array, but using any heterogeneous block-based storage. This all translates to significantly lower cost Hyper-V solutions that give customers a real reason to look at vSphere alternatives.
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