Server virtualization is a valuable way to save space, energy and money and to simplify management. But for all the advantages, there is still a major inefficiency: the ever-expanding need for disk storage to house and back up virtual machines
The Microsoft Hyper-V platform offers a couple of options to address this challenge. You can use Microsoft's Cluster Shared Volumes (CSVs) feature or third-party Hyper-V management -- which provides compelling advantages over the standard offering from Microsoft.
In this article, I highlight a few Hyper-V tools I have had experience with. The innovative companies that have created these offerings have worked to ease the storage misery within your virtual server environment.
Sanbolic Melio FS
Sanbolic Melio FS is a file system much like the VMware vStorage VMFS (or Virtual Machine File System), but it's for Hyper-V management. Melio FS functions such as a Clustered Shared Volumes (CSV), but with many more robust features, including the following:
- Full access. All nodes of your Hyper-V cluster can access and configure logical unit numbers (LUNs) formatted with Melio FS. There is no single coordinator node that allows access to the CSV.
- Quality of service. You can allocate guaranteed disk I/O bandwidth to a VM, a specific Virtual Hard Disk (VHD) or even a process. It allows for an even higher level of guaranteed service than is typically available within Hyper-V.
- Mirror storage across SANs. This feature enables a greater level of fault tolerance at the storage area network (SAN) level. A firmware update or SAN issue can no longer cause hundreds of VMs to be out of service. With mirrored storage across two SANs, all VMs will continue to run.
- Microsoft Volume Shadow Copy Service (VSS) support. Melio FS can create snapshots and backups of VMs at the volume or VHD level and make them accessible by VSS-aware backup products.
- Remote access. It's sometimes necessary to manually manipulate files associated with your VMs, and CSV does not offer this feature.
From a storage perspective, this Hyper-V management tool provides all the same benefits of a CSV for all of your clustered VMs. Melio FS gets away from the storage overhead associated with the one-LUN-per-VM architecture in Hyper-V R1 and offers many more advanced features.
The newest version of Melio FS was set to become available in January.
An up-and-coming Hyper-V tool from Virsto Software (to be named upon its February release) reduces the storage footprint of virtual environments through these three technologies:
- Thin provisioning. The Virsto product provisions only the space necessary without having to deploy the fully expanded VHD . This is the case for newly added VHDs and snapshot clones of VMs. The space savings in my environment could be more than 40%, which would help control storage costs.
- VM I/O blender. Hyper-V can technically do thin provisioning with dynamic VHD files. But if you have ever tried thin provisioning in a production environment, you know that the I/O performance is inadequate for most workloads. I have had to use fully provisioned, fixed-size VHD files, sacrificing space utilization for the I/O speed. Nirvana will offer both these features. Virsto's offering promises to more efficiently sort through the mass of random I/O requests that normally bombard your storage infrastructure.
- VM snapshots: The Virsto product can create multiple levels of snapshots that allow you to go back in time to a previous configuration. There is no noticeable degradation in performance, like there can be when Hyper-V creates Automatic Virtual Hard Disk (AVHD) files during this process.
Virsto's goal is to be hardware-agnostic, so none of these product features require specialized hardware. In my environment, the thin provisioning component alone would prove valuable in saving terabytes of SAN storage. And if reports of non-degrading I/O performance are true at the same time, it could translate into significant savings.
The Virsto Hyper-V management tool is currently in beta.
Data Domain Appliance Series
EMC's Data Domain Appliance Series is not directly associated with virtualization, but when coupled with a backup product that you might already own, it can provide significant space savings.
Its deduplication method looks at 8 KB blocks of data and compares them with other data it has already sequenced. If the data is the same as previously sequenced data, it is disregarded. If it is unique, it is written to disk. From a Hyper-V VHD perspective, think about all the blank space within a fixed VHD. That blank space is the same across all of your VHDs, so at a minimum you are backing up only the data within a fixed VHD file. During my testing, however, this deduplication process goes much deeper than just this free space.
With its ability to replicate some or all the data to another site, the Data Domain Appliance Series can ease some of your virtual storage pain -- at least from a backup perspective.
For years I have worked to slow the sprawl of physical servers in the data center, and I have seen the number of physical servers drop significantly. But as a side effect of this success, the need for additional disk resources has grown-- leading to terabytes of wasted disk storage and the purchase of faster SANs. These third-party Hyper-V management tools and storage appliances can help you bring these problems under control.
Do you have any other third-party storage apps you use in your virtual infrastructure? Email me.
About the expert
Rob McShinsky is a senior systems engineer at Dartmouth Hitchcock Medical Center in Lebanon, N.H., and has more
than 12 years of experience in the industry -- including a focus on server virtualization since
2004. He has been closely involved with Microsoft as an early adopter of Hyper-V and System Center
Virtual Machine Manager 2008, as well as a customer
reference. In addition, he blogs at VirtuallyAware.com, writing tips and documenting
experiences with various virtualization products.
This was first published in February 2010