Consolidating multiple physical machines onto one physical server that hosts multiple virtual machines (VMs) requires that organizations consider much more than just if the new server has sufficient processing, network bandwidth and memory to support the applications. Specifically, path and storage management issues can result when physical servers are virtualized which can preclude organizations from virtualizing some of their mission critical servers. However the recent announcement that Symantec now supports the movement of its Veritas Storage Foundation for Windows 5.1 from the child to the parent partition on Microsoft Hyper-V Server breaks through these issues and opens the door for organizations to virtualize all of their physical servers.
Symantec’s decision to move Storage Foundation from Hyper-V guests down to the Hyper-V parent was driven, in part, by calls that its support team was receiving from users in EMEA (Europe, Middle East and Asia) that were deploying Storage Foundation at the Hyper-V parent layer. These users needed software storage management features on their Windows platforms for campus clustering which, as part of the deployment, had a requirement for mirroring. These customers wanted to use software mirroring to abstract the storage team out of the solution so their system admin teams could manage the disaster recovery (DR) solutions without directly involving the storage admin team.
At the time that these customers moved Storage Foundation from the Hyper-V child to the parent, it was done unbeknownst to Symantec since Symantec did not officially support this configuration. Yet Symantec and its customers discovered some unexpected benefits when Storage Foundation was moved into the Hyper-V parent. Aside from the fact that it worked, it addressed a persistent problem that file system based server virtualization solutions like Microsoft Hyper-V currently present – the inability to provide advanced path and storage management features to guest VMs.
When storage volumes are presented by the storage system (either direct attached or via a storage network) and detected by the Microsoft Hyper-V parent, the Hyper-V parent virtualizes all of the storage. From this storage pool, Hyper-V parent administrators create multiple Microsoft Virtual Hard Drive (VHD) files. Each of these VHD files contains a partition of the Hyper-V parent’s storage pool is assigned to and then owned by that VM. The difficulty with this approach is that once a VHD is assigned to a VM, it becomes very difficult to perform any further advanced path and storage management features on that VM and the VM may lose some or all of these features that it previously possessed when it was a physical server.
Running Storage Foundation in the Hyper-V parent changes this. Storage Foundation turns the devices presented by the array into dynamic disk, creates dynamic volumes on the dynamic disk and formats these volumes with NTFS all within the Hyper-V parent. Hyper-V then places VHDs on these dynamic volumes which are presented to individual child VMs.
The new variable in this equation is that each and every VHD now sits atop of a Storage Foundation dynamic volume so the path and storage management features normally found in and managed on the guest VM are now located in and managed at the Hyper-V parent level.
This represents a major breakthrough in path and storage management for file system based server virtualization that Microsoft Hyper-V and Storage Foundation are the first to deliver to the best of my knowledge. A Microsoft Hyper-V server with Storage Foundation now gives each of its child VMs access to path and storage management features that they normally would have lost when they were virtualized (there are some exceptions when using iSCSI that I won’t get into here).
Storage Foundation can now communicate directly with the actual volumes of the underlying storage system as well as the physical server’s Fibre Channel (FC) host bus adaptors (HBAs). This keeps legacy path and storage management features remain intact since the VHD assigned to the VM is using a dynamic volume created by Storage Foundation that can deliver this functionality.
So what does this practically mean for end-users in the near term? Two things:
- Advanced path management for applications running in FC environments is back. Storage Foundation can now detect and communicate with the physical FC HBAs on the Hyper-V Server and send traffic from each VM down separate physical paths. This delivers load balancing and high availability for each VM on the Hyper-V server should a FC HBA fail or if a FC network path goes down. Further, if a FC HBA on the Hyper-V server starts to become congested, Storage Foundation can detect this congestion and route more of the I/O traffic down a less congested FC path.
- Administrators can now grow storage volumes containing a specific VM’s VHD or set of VHDs or even move that volume containing one or more VHDs to other storage without taking the VMs offline. Again, because each VHD is using Storage Foundation dynamic volumes beneath the surface, Storage Foundation’s functions are now extended and available to every VM on that Hyper-V server.
File system based server virtualization solutions such as Microsoft Hyper-V and VMware ESX server had, up to this point, faced a significant obstacle to overcome in terms of delivering the path and storage management features that organizations needed to justify virtualizing their mission-critical servers.
In this particular case, Symantec with the assistance of its customers in EMEA, accidently discovered the breakthrough that will make Microsoft Hyper-V a much more viable alternative to the VMware ESX server in the near term while laying the groundwork for some exciting new possibilities going forward. In a final blog entry in this series evaluating this new application for Storage Foundation for Windows 5.1, I’ll get into what new opportunities moving Storage Foundation for Windows in the Hyper-V creates for organizations.
Part 1 of this three part series examines how file based server virtualization operating systems have failed to address high availability and performance requirements of certain applications and how Symantec Storage Foundation for Windows is addressing that in Microsoft Windows Hyper-V.
in this three part series examines how moving Storage Foundation for
Windows into the Hyper-V parent addresses some current issues around
thinly provisioned volumes as well as how Symantec keeps the licensing
for Storage Foundation for Windows attractive.