In addition to cost-savings derived from improved hardware utilization efficiencies, SANs were also supposed to deliver significant labor- related cost savings through improved management. The ENSA SAN advocates predicted an intelligent and largely self-managing infrastructure whose growth could be managed easily by a fixed number of staff. This value proposition remains unrealized in current SANs. By all accounts, using current tools and techniques, the most storage a single administrator can manage is approximately 300 to 500 GB. This number increases substantially when all storage arrays are homogeneous (as white papers commissioned from analysts by most array vendors often conclude). However, the reason has nothing to do with the storage topology. Rather, increased GB per administrator is a function of the efficacy of storage management software. If all deployed storage arrays are from a single vendor, the vendor's own configuration and management "point" software can be used to manage the products as a whole. The gain in GB per administrator has little or nothing to do with SANs, but with homogeneous infrastructure. The management of heterogeneous FC SANs, by contrast, continues to be a " kludge ." Part of the reason has to do with the lack of a "service" within the Fibre Channel protocol for performing in- band or in-the-wire management. When it was first invented at IBM, the Fibre Channel protocol was conceived as little more than a serial storage interconnect replacement for a SCSI parallel bus. Designers are fond of saying that they did not set out to create a network protocol, just a serial interconnect. Thus, "IP stack-like functions," such as in-band management and in-band security, were deliberately excluded from the Fibre Channel protocol. The Fibre Channel Industry Association, in a draft white paper detailing the roadmap for the protocol in 2000, recognized this deficit and stated that it was working to add in additional services to make the protocol more "network-like" in the future. [3] Whether or not Fibre Channel is, in fact, a network is a subject for debate among intelligent people in the industry. Howard Goldstein, a good guy and well-known storage consultant and trainer, offers a perspective that is somewhat contrary to this book. Out of deference to Howard, it is being printed here in its entirety.
Goldstein's perspective offers one of the most exhaustive efforts to rationalize the FC-as-network view of so many vendors in the FC community. According to him, even an effort to develop a channel interconnect can inadvertently lead to the creation of something else. He is fond of saying that, just as the fellow who developed "sticky notes" did not originally set out to develop a detachable/re-attachable glue, IBM invented a network architecture without meaning to. That alone does not invalidate the result as a network. However, Goldstein does agree that certain services were not originally provided in FC that are taken for granted in other messaging networks. Even where enhancements have been made to the protocol through subsequent standards body development efforts, they have not been seized upon by the industry or implemented at all in a standard way. In the absence of a native in-band management service, the FC SANs deployed today are actually a hybrid of a Fibre Channel protocol "fabric" ”basically, a switched, serial, storage interconnect linking servers and storage devices and providing data transport services ”and an IP network that also interconnects all SAN elements (server host bus adapters, switches, and storage controllers) to carry SAN management traffic (see Figure 3-7). In disagreement with Goldstein's conclusion, this author must conclude that it is oxymoronic for FC to ever have been used as the foundation for a storage network. Figure 3-7. The FC SAN topology ”A "kludge."
In fact, the lack of standards-based, in-band services in FC SAN implementations also accounts for the fact that heterogeneous FC SANs offer little improvement over heterogeneous server-attached configurations in terms of the number of GB that an individual storage administrator can manage. Until recently, those deploying heterogeneous SANs had enormous difficulty even with the low-level task of "discovering" heterogeneous devices in the same fabric. Vendors seemed to be going out of their way to ensure that a competitor's hardware could not be discovered or used by the switches of their preferred SAN switch-maker. SAN switch- makers seemed to be unwilling to recognize or interoperate with their competitor's switch product or with host bus adapters that were not part of their vendor cadre. Today, there has been some improvement in this space, with HBA vendors agreeing to a quasi-standard device driver and some large array vendors cooperating to create "Bluefin," an object-oriented messaging interface specification that links distributed management applications with device management support and enables the discovery of different arrays in the same fabric. It remains to be seen how well these cooperative arrangements will stand the test of time and the proprietary forces driving the industry to greater and greater Balkanization. If the tenure of recent application programming interface (API) swapping arrangements between vendors is any indication of the life expectancy of such surrogate services, the management of FC SANs will likely remain a headache for storage administrators for the foreseeable future. Even with discovery issues to some degree resolved, storage management ”defined here as the cost-efficient provisioning of data across storage resources to meet the data-storage, data-access , and data-protection requirements as determined by business applications and end-users ”entails significantly greater intelligence than contemporary tools provide. FC SANs, far from making storage management easier and reducing the labor costs associated with this activity, have actually contributed complexity and cost in most environments. The exceptions are homogeneous SANs created from the products of a select vendor cadre. However, in the final analysis, it is not the FC SAN that makes this infrastructure more manageable by fewer administrators, but the homogeneity of the configuration. |