Storage Service At The Hypervisor

In our last entry we discussed what storage services are and reviewed the traditional manner in which they are delivered. They are the capabilities that make a storage system more than just an array and this intelligence typically lives on the storage controllers. There are several alternative ways to deliver these services and one of the newest is to leverage server virtualization. Storage service at the hypervisor may be a disruptor of the traditional storage deployment model.In its most basic form, storage services in a virtualized environment can come from companies running the services as a virtual machine. Taking the intelligence off of the storage controller and moving it into a virtual machine. Companies like HP via their LeftHand Networks group, FalconStor, DataCore, NexentaStor and others are all providing this capability. As a result storage that would normally be considered locally attached, meaning it is installed inside or attached to the virtual host, is now able to be presented as shared storage not only across the virtualized cluster but in many cases to non-virtualized hosts outside of the cluster.

Most of these solutions deliver on the complete range of software service capabilities that you would expect; snapshots, replication, cloning. Some will leverage the RAID capabilities of the attached storage. Others will leverage the RAID capabilities of the hardware attached to the host.

Another angle that we see developing in this space is companies that enhance what is already there. For example Virsto works with Microsoft Hyper-V to provide extended storage services to that platform. We expect software like this that will work with the hypervisor to extend its capabilities to become more common place. Software like this will focus on enhancing the snapshot capabilities of the hypervisors so that multiple snapshots do not effect performance, enhance storage I/O control so that writes to disk are more organized and simplifying storage provisioning so that it is more of a natural extension of the hypervisor.

Finally, especially in the small to medium sized data center, solutions that are direct attached but can still deliver on the key virtualization feature of server migration will appeal. Everyone gets direct attached storage, there is almost nothing to learn. The challenge is of course being able to move those servers to different hosts. An example of solving this problem is offered by companies like CORAID which delivers storage connectivity over ethernet. ATA over Ethernet (AoE) uses ethernet to connect to storage similar to how you use fibre today. The exception is that this is a SAN (block level) protocol like iSCSI/FC/FCoE style connection meaning the storage is allocated to one particular VM. This reduces drive contention since you can configure so that only one VM is allocated to each volume. However, since it is on an ethernet network it still can be logically detached from one physical host and then reattached to another.

The impact the server virtualization is going to have on storage is just now being felt. The above technologies are just a few of the examples of how storage companies that leverage the virtual infrastructure are going to change the way we manage and acquire storage storage.

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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.