While there are many benefits to NAS architectures, one of the primary detractors has been the lack of scalability or the ability to dynamically expand the storage without having to upgrade the NAS server. What this has led to is the same environment that IT tried to avoid by moving to network storage architectures - the proliferation of NAS servers with separate management interfaces, thereby reducing the management benefits of consolidated storage. Fortunately, vendors are developing solutions to this problem.
One solution offered by NetworkAppliance (http://www.netapp.com/) is DataFabric Manager, which manages multiple NetApp NAS filers. This tool automatically discovers NetApp servers to give a unified view and centralized management capabilities.
While this is a step in the right direction for NetworkAppliance, the solution is homogeneous. Today, there are other software management products on the market that will provide monitoring as well as some native management capabilities across many storage architectures such as direct-attached storage, storage-area networks (SAN), and NAS. One such company, whose product became generally available at the end of May, is StorageNetworks (http://www.storagenetworks.com/) with its STORos management solution.
NetworkAppliance has also increased the amount of storage supported by its high-end filers to 18 terabytes (2 - 9 terabyte filers in a clustered configuration). And now with its NearStore products that are targeted at the backup and archive markets, NetworkAppliance can scale to 96 terabytes of storage.
However, the company has yet to take advantage of the scalability capabilities afforded by the back-end Fibre Channel through the use of a SAN. SAN storage companies, such as EMC, Compaq (I mean HP) and XIOtech (http://www.xiotech.com/), are either beginning to partner with companies creating NAS filers to provide scalable storage architectures behind the NAS filer, or creating their own NAS filers with SAN at the back end. The latter provides the best of both worlds: shared files and consolidated storage management.
Another approach for scaling NAS storage within a single management domain is by aggregating NAS filers using a distributed file system. Companies such as LeftHand Networks (http://www.lefthandnetworks.com/) and Tricord (http://www.tricord.com/) provide this type of scalability. As you add filers to the grid or cluster, the associated storage is added to the storage pool automatically, quite often with the data being distributed over all the filers within the grid. This not only provides scalability but high-availability as well.
So, you ask, what is the SAN/NAS convergence all about? Is it placing NAS filers, as another application server, within the SAN? Well, partially. This has certainly been the first step. However, solutions such as ADIC's CentraVision (http://www.adic.com/) or SGI's CxFS (http://www.sgi.com/) are far closer to converging SAN and NAS. Both of these products move the bulk of the file system off the server and into the SAN. This preserves the block-level performance of the SAN but allows for a shared file system name space within the SAN. Architecturally, when you move the file system into the SAN, it allows for heterogeneous support of servers and storage, consolidating file system data management as well as storage management.
The research Enterprise Management Associates has compiled consistently shows that efficient storage management for storage growth and easing day-to-day operations are top issues in the IT environment. For file-based operations, vendors are starting to produce significant value, with their solutions, in these areas.