IP Storage Networking: Straight to the Core

Storage resource management (SRM) is the second component of infrastructure-focused SAN management. While storage network management (SNM) focuses primarily on the connectivity and combinations of storage devices on a network, SRM focuses on the individual devices and the ability to see and modify those devices from a central location. SRM may also be referred to as device management, an appropriate term , given the focus, and an easy way to distinguish from SNM. The primary benefit of SRM is the ability to make more effective use of the resources within an organization, specifically storage capacity and resource efficiency, as outlined at the end of this section.

For clarification purposes, we divide SRM categories into devices and subsystems. Devices are those elements within the overall storage infrastructure that provide access to storage, while subsystems house the actual disk or tape media.

3.3.1 Device Management

In the device category, SRM looks remarkably similar to SNM. Devices under an SRM application may include HBAs, switches, and routers. The SRM application provides a unified view of these devices and the ability to make some changes. In many cases, the SRM application will simply point to the device-specific management interface embedded within the product.

Device management features of SRM include discovery, topology mapping, and configuration planning. These tools provide SRM applications the information to help find potential problems and recommend solutions. Zoning is typically not included in SRM packages.

The primary difference between device management across SNM and SRM applications is the integration with additional multivendor infrastructure. For SRM applications, the visibility typically extends deeper into the subsystems category.

3.3.2 Subsystem Management

SRM features shine when used in large installations of disparate storage subsystems that require centralized administration. In these environments, an SRM application takes a logical view of the storage configuration and provides administrators a clearinghouse to receive information and implement changes.

SRM applications discover storage within the overall infrastructure and provide logical-to-physical maps of storage utilization, such as which servers are using which storage. Further, SRM applications identify operational file systems and file-level detail of such storage. For block-based storage, SRM locates volume groups and provides volume mapping visibility within and across subsystems.

This level of detail can be used by storage administrators to understand asset allocation and identify usage patterns across applications, departments, and individuals. From this viewpoint, administrators now have the required knowledge to drive decisions about optimized storage use within the organization. This leads to the establishment of policies such as quota management, covered in Section 3.5, "Storage Policy Management."

Even with storage resource management focused on the subsystems side, LUN and RAID creation and modification still remain within the subsystem. These features may be accessed through centralized interfaces; however, this basic level of disk aggregation can be effectively accomplished only by the subsystem vendor.

3.3.3 Resource Efficiency

SRM information allows administrators to see the efficiency of their storage resources, such as the amount of storage used compared to the total amount available in the array. This top-level view helps quickly pinpoint overutilized or underutilized storage, allowing administrators to appropriate respond. Additionally, SRM views of the data itself can provide efficiency clues. For example, closer examination of file data may reveal rampant file revision propagation or an absurdly large collection of .mp3 or video files. Once this information is collected and examined, administrators can appropriately respond.

Identifying which servers and applications address which storage helps match the logical and physical pictures. If the accounting department is using 75 percent of the capacity of an array in another building, it may make sense to have that array located within the accounting department yet still available through the storage network to the rest of the organization.

3.3.4 Capacity Planning

Using historical information from SRM applications, specifically trend analysis, administrators can plan for storage capacity more effectively. With visibility into the actual data, including the types of files and applications related to growing volumes , SRM applications can plot and chart areas of future storage growth. Based on such information, administrators can make more accurate decisions based on more than a simple look at the total number of terabytes within the organization.

In addition to helping predict future capacity needs, SRM can help administrators make use of existing capacity, thereby minimizing new storage purchases. For example, the duration for saved email archives can be weighed against the cost of new capacity.

3.3.5 Integration with Other Storage Management Applications

For SRM to be truly effective, the monitoring functions must be incorporated with other functions of storage management, such as data coordination, protection, and policy management. Administrators can begin with basic questions such as the type of storage data, primary users, usage habits, access times and durations, and storage location. From there, policies and actions can be put in place to maximize efficiency, cap reckless data accumulation, and automatically provision and protect storage as needed.