Out-of band SAN appliances allow for independent flow of data between servers and storages since it does not function within the data path (InfoWorld, 2001). In addition, execution of management functions by these appliances is independent of application servers, a factor which dictates for having host drives. This has the implication that the positioning of an out-band SAN appliance posses performance concerns in the system (InfoWorld, 2001).
Another implication is that increase in the number of server in such a system complicates administration issues. Still, out-of band SAN appliances have its meta-data and control operations separate from the data path. This coupled with the need for having a driver at each host frees the host to engage only in transferring data to and from the storage. Nevertheless, this configuration has the advantage of caching due to the request time delays involved in linking data path information and the appliance for processing.
On the other hand, in-band SAN appliances employ a single device for executing all the basic storage management functions namely; data path, control operations, and meta-data management (Kornfeld, 2001). This has the implication that no additional driver software is needed in the host. Also, this enhances scalability of the SAN system. However, this limits the application of in-band SAN appliances in a busy SAN since both meta-data and control operations share the same data path.
Despite this, in-band SAN appliances enjoy the privilege of allowing for caching and clustering (InfoWorld, 2001). In addition, being a single device, in-band SAN appliances boast of low cost of implementation and ease of administration (Kornfeld, 2001). Therefore, both in-band and out-of-band SAN appliances have advantages as well as disadvantages. Considerations before choice of a SAN appliance should thus be based on the needs in the particular organization.