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Device discovery
SRM vendors use three primary approaches--standards, vendor storage device APIs and server agents--to improve SRM tools' delivery of heterogeneous storage device discovery and management.

THE STATE OF SMI-S
The Storage Management Initiative Specification (SMI-S) is often viewed as the technology foundation that will solve many storage management problems. But no storage resource management (SRM) vendor uses SMI-S exclusively, and most find it problematic at best. Ash Ashutosh, co-founder and former executive vice president and CTO at AppIQ, and now current CTO of storage management software at Hewlett-Packard (HP) Co.,

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says SMI-S came out of the gate with unrealistic expectations. "People expected it to solve interoperability problems between devices and that was never the objective of SMI-S," he says. "Rather, it was to provide a unified way of managing storage and in that vein SMI-S has been successful."

However, Ashutosh says there isn't a very rigorous testing procedure for hardware products that claim to support SMI-S. Without more stringent testing methods, vendors' interpretations of the standards diverge widely, although Ashutosh notes this is a loophole the Storage Networking Industry Association is trying to close. He hopes vendors will participate in HP's OpenIQ program, which lets hardware vendors quickly provide a front-end, SMI-S-compliant interface to their storage device for management software.
In theory, the simplest way to discover and manage devices in a heterogeneous storage environment is to use storage standards such as SMI-S, Web-Based Enterprise Management (WBEM) and Windows Management Instrumentation (WMI). To communicate with storage devices, SRM tools send SMI-S commands over IP to the management ports on storage devices. Connecting storage devices to a corporate LAN should allow an SRM product to discover them using SMI-S.

However, some older storage arrays, such as EMC's Symmetrix, are managed through an FC interface rather than a TCP/IP interface, so these devices require a different technique to be discovered and managed. In addition, each vendor has a unique interpretation of SMI-S as well as different releases of SMI-S code on the market. Hitachi Data Systems (HDS) began implementing SMI-S standards on its arrays three years ago; however, older HDS arrays such as the 7700 may not support SMI-S (see "The state of SMI-S," at right).

With SMI-S storage standards still maturing, SRM vendors rely on APIs provided by storage device vendors to discover and manage those devices. But this approach presents its own set of problems. For example, Softek's Storage Manager can discover arrays from EMC and HDS, but its implementation calls for users to install APIs for each of these vendor's arrays on a server--preferably on servers other than Softek's management server.

But the concerns don't end there. The server hosting EMC's APIs will need FC connectivity to all of the Symmetrix arrays it needs to discover and manage. And not every version of EMC's APIs supports all of its arrays. Users who wish to use EMC's SYMAPI to discover Clariion arrays over TCP/IP will need to use Version 6.x of SYMAPI. But if you upgrade to 6.x and you're also using EMC ControlCenter on that server to host the SYMAPI software, you'll need to upgrade your version of ControlCenter to at least Version 5.2.

One alternative to using the native APIs provided by storage vendors is to wait until storage vendors adopt interfaces like HP's OpenIQ middleware, which provides a common set of APIs. This technique gives storage vendors the option to purchase a middleware package and use it as a type of software wrapper around their storage array to make it standards-compliant. However, the likelihood of any middleware approach working is dubious until it's endorsed as a standard and implemented by major storage hardware vendors.

The final way SRM products discover and manage storage environments is through the deployment of server agents. These agents can deliver four principal pieces of information: the physical hardware on the server such as FC HBAs, LUNs discovered by each HBA and server and the volume groups they're in, filelevel information and database information. Not every vendor's agent installs the same way or delivers the same functionality. Agents from CA, Northern Parklife and Softek take only a few minutes to install and deliver file-level information. Conversely, EMC's ControlCenter agent can provide everything from HBA information to the layout of database table spaces on attached Symmetrix arrays, but it can take 30 minutes or longer to install and configure on each server, depending on how many options are installed.

This was first published in January 2006

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