There are already several ways to front-end a SAN with NAS technology. Most people have been calling this SAN-NAS Convergence. In reality, the implementations are truly front-end type of solutions. There are others being proposed/developed that have yet to reach the market. Unfortunately, there's quite a bit of marketing hype and misinformation here where much of the terminology is being applied differently than most of us would agree with.
Some of the solutions available today include using a NAS Gateway, a head, executor or controller depending on the individual marketing-inspired naming to serve as a NAS device on an Ethernet network with the actual storage for the NAS device existing in the SAN. Remember, a NAS device translates a file-level access from a remote access to a local block I/O access. There are several products available today from IBM, EMC, Compaq, HP, etc. (I'm sure I've overlooked several). There are advantages in management and capacity in this type of solution and those vendors have information available to explain the value.
Another solution that has been available for quite some time is the metadata server approach where data is accessed using remote file protocols such as NFS and CIFS with the metadata server responding to the redirector software on the client (requestor) with the location of the information on the storage attached to the SAN and the client does block I/O to access the data, thereby offloading the Ethernet network and achieving the higher SAN speeds. One of the early implementations of this was Mercury SANergy that IBM bought and offers under the Tivoli label. EMC's Highroad and ADIC's CentraVision are solutions that work relatively the same way. There are other solutions like this as well.
Yet another solution is to have a distributed file system to treat data in the SAN as globally attached file systems so there is no need for remote file system access, it can be perceived as local file system access. VERITAS has more than one solution in this area and other vendors may have as well.
Many of these solutions may start out at small vendors but often, the successful ones get purchased by larger companies. Looking at the smaller companies and their solutions, we always try to evaluate whether they are candidates to be purchased and their long-term economic viability. The larger companies have greater sales and distribution outlets as well as the name recognition and long-term product support commitments.
Evaluator Group, Inc.
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This was first published in October 2001