Fabric-based intelligence: but do a reality check on the switches before you buy - Disaster Recovery

Computer Technology Review, August, 2003 by Christine Taylor Chudnow

Switch vendors are actively adding more intelligence at the fabric level. What that intelligence should be is open to debate (and different vendors are promoting different types) but most agree that managing the SAN through the infrastructure is very promising. Development is generally centering on copy and move functions, such as replication and remote mirroring; virtualization, provisioning and storage management; and internet-working and utility-based models. With so much active development going on, both established switch makers and starry-eyed start-ups are preaching the benefits of concentrating storage management and protection in the infrastructure. The question is: Is this a good thing?

Rob Emsley, HP's product marketing manager, Network Storage Solutions division, thinks there's not really one right answer to that. "Clearly, within the storage area networking industry, the fabric is a core component of the environment. It's like the hub in the wheel--everything is connected with it. The power of the network is directly proportional to the number of elements connected to the network." The value of the SAN increases according to the number of connections. That's why fabric-based intelligence gets so much focus: people recognize that network management and the capabilities of the network are key components to its value. Since Fibre Channel SANs are more expensive and complex than IP networks, SAN buyers are looking for ways of getting maximum value out of the investment. Adding capabilities to the environment multiplies the value of the ROI dollars.

Sounds good, and it can be--but the corollary to concentrating intelligence in the fabric is the absolute need to protect that fabric. Once you start using switches for more and more management functions, administrators must make sure they failover and replicate those switches, as well. If there's a bank of ports or a large director switch that's handling storage resource management, archiving and remote mirroring, those pieces had better be fully redundant with no single points of failure. Given price, complexity and risk levels, many vendors--including established switch vendors--are still leaving framework management to software. For example, Brocade puts robust security functionality into its switches, but leaves management to storage management software.

Still, most switch makers are charging ahead with intelligence development. Mark Stratton, McData's director of Solutions and Alliances programs, describes the switch vendor's viewpoint. "We're looking at managing more of what's in the fabric, also providing more information about relationships of what we're managing. We'll continue to be as aggressive as we can in this space." Switch intelligence vendors are primarily concentrating on several different developments, including copying, storage management, and utility storage computing.

Copy and move: These functions include replication, remote mirroring, and online backup. They also control tiered storage, which migrates data to different storage targets depending on characteristics.

Storage management: Virtualization is a big development center for switch makers, since virtualization significantly improves volume management and provisioning between different storage arrays.

Utility storage computing: The utility model sees the network infrastructure as a dynamic storage manager instead of a costly investment.

Copying

Fibre Channel fabric is well suited for copy and move functions, the foundation of backup and replication, These functions are largely proprietary today, and dependent on different vendors' backup and replication applications. By putting the copying mechanism in the fabric rather than relying on the sub-system host, it is possible to have a heterogeneous, open-based connectivity approach to replicate, mirror, and backup between arrays on local and remote sites. The fabric may control such functions as replication, remote mirroring, and tiered storage schemes.

Tiered storage operations migrate data to different storage targets based on policies. For example, a production database would retain its active data on high-end arrays, while a tiered storage manager would archive inactive data onto less expensive ATA disk. Given data parameters, some of the data would remain on ATA indefinitely, while other data would in turn migrate to online tape libraries or off-line vault storage. A number of software packages do this today, but some switch intelligence developers believe that the fabric would handle tiered storage much more efficiently in open environments.

Storage Management

Storage administrators want and need to automate repetitive tasks with storage management tools. Software already does this, but switch makers believe that the fabric is better suited to managing SAN-wide storage than host-based applications. For example, virtualization is the foundation for automated provisioning. Some switch developers prefer to see virtualization in the physical data path, where it can dynamically allocate storage to a pool of shared resources. Virtualization-capable switches might contain a policy engine that manages layers of sub-policies, which in turn automate provisioning between the arrays. Stratton added, "We're looking at managing more of what's in the fabric, also providing more information about relationships of what we're managing. We'll continue to be as aggressive as we can in this space."