10.5 The Common Information Model (CIM) (Bluefin)

The storage networking industry has been struggling with management issues since its inception. In the evolution of a new technology, basic functionality must be developed before advanced services can be implemented.

For SAN technology in particular, the development of standardized management, quality of service, and security services has trailed far behind the deployment of infrastructure and SAN-enabled applications. Consequently, customers are handed an assortment of installation CDs and manuals for different device managers and storage utilities, and they are expected to administer a single SAN through a myriad of management consoles.

Although hardware vendors may use SNMP, HTTP, or Telnet to configure and monitor their products, value-added management may be provided by proprietary APIs. APIs enable dynamic and granular management but are vendor-specific. Proprietary APIs have thus become a tool for maintaining a competitive advantage in the market, as well as a means to exclude others from providing products that can be managed from a common platform. The situation is not improved by "gentlemen's agreements" between dominant vendors to exchange their proprietary API information so that they can manage each other's products. This simply expands the circle of market influence from individual vendors to vendor affinity groups but does not provide the customer an open systems solution.

In response to single-vendor initiatives and to customer dissatisfaction with continued proprietary offerings, the storage networking industry has rallied around an open systems management proposal based on the Common Information Model. The CIM initiative for storage networking (known as Bluefin in its draft form) will provide a standards-based alternative to proprietary SAN management and may ultimately achieve the goal of comprehensive management of multivendor storage networks from a single console.

The Common Information Model has been under construction for some time as an object-oriented framework for managing virtually anything connected to a network. CIM development in general has been led by the Distributed Management Task Force (DMTF), whereas storage network-specific CIM has been developed within the Storage Networking Industry Association.

CIM provides a common management interface under the umbrella of Web Based Enterprise Management, or WBEM. WBEM leverages the ubiquity of Internet protocols and browsers to provide enterprise-wide management of all IT resources. This enables a commonly deployed and essentially free user interface for a comprehensive and sophisticated management infrastructure.

The CIM specification maps existing management protocols such as SNMP and APIs to a structured, object-based model. Because the CIM specification is all-encompassing, it divides the world of managed entities into schemas. CIM schemas are organized frameworks that define systems, applications, networks, devices, and physical elements to be managed. SAN management thus involves the definition of schemas that are specific to storage and storage transport management.

As shown in Figure 10-7, CIM sits between managed devices and the upper-layer management application. To provide backward compatibility, SNMP and other management protocols can be accessed via an entity mapping. This enables the current generation of SNMP-based devices to be grandfathered into a CIM-based management framework. Alternatively, vendors can implement standardized APIs within their products that communicate directly to the common interface. CIM information is formatted via Exten sible Markup Language (XML) and delivered to a browser using HTTP over TCP/IP. Use of standard Internet tools enables WBEM/CIM to be run on any operating system and any IP infrastructure.

Figure 10-7. Common Interface Model for multivendor, cross-platform management

For storage networking, the CIM model is implemented through agents that can be embedded in SAN hardware or software products. An HBA, for example, can support a CIM agent that provides standard HBA-specific information in the structure of an object class HBA. For devices that are not CIM-compliant, a proxy server can solicit status and configuration information through standard SNMP or HTTP protocols and present that data in CIM format. Agents report to clients, which are distributed management applications that gather and rationalize the aggregated management data. The management client can implement a CIM object manager (CIMOM) to manage a diversity of storage devices and resources.

Standardization of CIM for storage networking is being assumed by the SNIA. Standards development is expensive, both in terms of actual costs for technical editors and standards compliance testing, and in terms of volunteer resources from contributing companies and individuals. Achieving an open systems solution for management of SAN applications, subsystems, and devices, however, will remove one of the major impediments to SAN adoption and will enable more customers to realize the benefits of shared storage.