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Server Virtualization's Encapsulation And Its Impact On Storage

To say that server virtualization changes everything is an understatement. In storage though I don't think we understand or give credit to just how much of a game changer storage virtualization really is. For storage managers and backup administrators it has brought new capabilities, new requirements and new problems to solve.
To say that server virtualization changes everything is an understatement. In storage though I don't think we understand or give credit to just how much of a game changer storage virtualization really is. For storage managers and backup administrators it has brought new capabilities, new requirements and new problems to solve.The biggest change is the encapsulation of an entire server into a single file. That file now justifies, more so than ever, the use of shared storage so that the encapsulated server file can be accessed by multiple physical servers at any time. Shared storage is the foundation that server virtualization needs to have the ability to migrate virtual machines between physical servers to increase server up time and load balance performance. This has lead businesses to implement and use shared storage sooner than ever. This early move to shared storage has created a whole new level of storage systems that leverage either iSCSI or Network Attached Storage (NAS) to drive down costs and increase platform simplicity.

This is especially true in the NAS vendor community. The ability to host the encapsulated servers on an NFS share opened NAS systems up to a whole new market. Instead of being just file servers they are now "server" servers. As we discussed in our article "Using NFS for Server Virtualization" using NFS to host the encapsulated server image is becoming much more widely accepted and should be considered along with iSCSI and ATA over Ethernet as a way to leverage the existing network infrastructure for storing and sharing virtual machine images as well as simplifying the storage management component of server virtualization.

As the virtual environment grows it leads to fewer physical servers with many virtual machines running on them. This creates a highly randomized I/O problem in the many data centers that used to only occur in high performance computing environments. The need to solve the storage I/O problems caused by server virtualization has lead to the development of scalable high performing storage systems. They are also driving further SSD adoption to augment existing storage systems as we discussed in our article "Enhancing Server And Desktop Virtualization With SSD". Solid State storage addresses much of the storage I/O problem by adding a zero latent tier of storage that is highly responsive to random workloads.

Faster storage systems can only deliver those improved performance numbers if the network can move that information between the virtual host and the storage subsystem. This is leading to more intelligent networking cards that not only deliver a raw speed improvement via 10Gb Ethernet or 16GB Fibre Channel but also have some intelligence that allows for prioritization of specific virtual machine workloads. Leveraging technologies like N_Port ID Virtualization (NPIV) and providing a card level Quality of Service (QoS) is going to be critical to meet application level server level agreements (SLA). When we can guarantee performance levels it will allow the virtualization of more mission critical applications and denser VM to physical host configurations.

The encapsulation of server images has also changed dramatically the approach to data protection. In our next entry we will look at how the data protection industry is fundamentally changing because of the encapsulation of servers.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.

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