A stand alone NAS appliance provides many of the features and capabilities that storage managers need and expect in a file server replacement product like snapshots and thin provisioning. The issue is that these systems are outside of the virtual infrastructure which can lead to additional management overhead as well as not being able to leverage the load balancing and availability provided by the virtual environment. The stand alone NAS appliance is often coupled with its own storage, which represents a separate pool of storage to be managed and protected. It also can't leverage the inherent capabilities of the virtual infrastructure. For example, if there’s a need for a faster NAS head, a new one must be purchased. NAS as a virtual machine, on the other hand, could leverage VM migration to move to a faster, more capable server. This is especially valuable if the increased performance demand is only temporary.

An alternative is to create Linux or Windows VMs that act as file servers. While this is a common solution for the block based virtual environment it can also lead to problems. First is the challenge of file server sprawl. Although virtual, having to manage an increasing number of file servers, each with their own virtual storage pools, increases the administrative burden. Ironically, an original use case for NAS systems was to address file server sprawl, something that can be worse in the virtual environment. In addition, standard operating system loads are not optimized for file serving performance. In either operating system choice there are also concerns about cross platform support as neither operating system handles the other operating system’s files perfectly.

Another challenge, particularly in the case of Windows, is that a full blown operating system image is being loaded to handle the file sharing task. This means that more resources have to be set aside for each of the instances than really should be needed. Using a full operating system also includes the expense of additional Windows licenses and the appropriate user license count.

Controlling capacity growth is another big challenge with the file server or NAS environments. This is being caused by the increasing number of users that are creating an increasing number of more complex and media rich documents. Then also it is compounded by these files being collaborated on within the network infrastructure. Multiple versions of a similar copy of the file are saved in user’s directories. All of this adds to unprecedented growth in storage consumption. Not only does this mean capacity is needed sooner but in the virtual environment it must come from the most expensive source, the SAN. In reality most of these files and their versions are only active for a very short timeframe and then go dormant. However, they are rarely deleted "just in case" they are needed again. A virtual NAS could leverage cloud storage to use a small amount of SAN resources for the active set of data and use cloud storage as the repository for all those "just in case" files.

Cloud enabled virtual NAS services may be a viable alternative for providing file services in these types of virtual infrastructures. A virtual NAS appliance can bridge the gap between the stand alone appliance and the OS-specific virtual machine approach. It can provide the complete range of NAS services like a stand alone appliance, yet run as a virtual machine, leveraging that infrastructure and its storage.

A virtual NAS appliance greatly simplifies the management of providing file services to users. First, the function is managed through the same interface as the rest of the virtual servers in the environment. Second, the virtual NAS can be shifted from physical host to physical host for performance or maintenance, as well as for disaster recovery. Revisiting the above example, a temporary need for higher performance could be easily addressed by a virtual NAS. As peak loading occurs, the NAS instance could be shifted to a more capable physical host with greater bandwidth and then migrated back as needed. If the virtual NAS required access to faster storage, capabilities like storage VMotion could migrate the virtual machine to a faster tier of storage for as long as the demand existed.

A virtual NAS will require more than just a NAS application re-compiled to run as a virtual machine, but a NAS appliance designed from the ground up to be a virtual machine. The advantage of starting with the virtual infrastructure in mind is that the inherent capabilities of that infrastructure can be leveraged. This means that complex coding that a stand alone system would require can be left out of the development effort. Capabilities like snapshots, high availability and disaster recovery can all be simplified by using what is already available in the virtual infrastructure. Even advanced capabilities such as auto-tiering can be addressed to some extent by using features like VMware's Storage VMotion. By creating a NAS appliance to be virtual from the beginning allows a developer to keep the resource requirements of the NAS small and focus its precious development resources in other areas.

Another advantage of a NAS designed for a virtual environment relates to the concept of ‘unified storage’. This is the capability that many NAS vendors are adding to their products by providing block services in addition to NAS services. Since virtual infrastructures are most often block-storage based to begin with, adding virtual NAS services essentially makes it a ‘unified storage’ infrastructure. The difference is that the virtual NAS appliance doesn’t have to include block services itself, greatly simplifying development and reducing cost. A recent VMware report indicates that a majority of virtual infrastructures are block based, so again, adding NAS services virtually to those infrastructures may be an ideal match.

An example of taking advantage of what the virtual infrastructure already provides and focusing development efforts on new capabilities is leveraging cloud storage as Nasuni has done with their Filer. As covered in Storage Switzerland's latest lab test drive, the Nasuni Filer automatically replicates data to the cloud provider specified every hour. The local storage is essentially a cache that never grows beyond a user-selectable size. As a result a virtual NAS like Nasuni's can also address one of the other top issues when managing file servers - data growth. Only the active and near-active data is stored in the cache, keeping capacity and performance demands under control. Many organizations find that a 64GB local cache is more than sufficient for day to day storage needs, a space so small that a mirrored set of solid state disk drives could be used to provide very high speed local access and affordable long term retention in the cloud.

Nasuni is a client of Storage Switzerland

George Crump, Senior Analyst