Better grade for smart switches

For many years, vendors have been promoting intelligent storage switches, particularly for virtualization projects. Initial implementations, however, relied mainly on appliances that created performance bottlenecks and were application-specific and difficult to scale. As a result, end users have been slow to adopt those so-called smarter solutions.

"I don't see any real intelligence yet," says Chris M. Christian, senior design lead SAN architect at Norfolk Southern, a freight railway company. "Advanced intelligence features probably won't arrive till at least the summer, and maybe even later."

Though the products may not be ready quite yet, more intelligence has been added, and a lot more is on the immediate horizon. The driver? The frenzy surrounding information life-cycle management (ILM), which requires a rapid ramp-up in intelligence in order to move data around, regardless of the disk array, platform or servers. As a result, products are now coming onto the market that offer additional switch-based services and hold the promise of easing the storage management burden.

"Moving storage functionality into the switch offers the potential for long-overdue management relief when compared to traditional, host-based techniques," says Fred Moore, president of Horison Information Strategies, a storage consultancy. "Many applications are ideal for this, including virtualization, volume management, backup, replication, storage resource management, hierarchical storage management and security."

Compared with traditional data communications switches and routers, storage switches have always had to provide additional functions that could be classified as intelligent.

Device discovery, for example, is essential for storage networking. Servers are initiators of storage transactions, but storage arrays are passive targets. For servers to find and establish connections with storage arrays, the fabric switch provides fabric log-on services and a simple name server. Once storage devices are registered with the fabric, servers may query the switch to discover potential targets. Likewise, fabric zoning and the mapping and masking of logical unit numbers are intelligent functions designed to ensure that only authorized devices are allowed to communicate across the fabric.

The current wave of intelligence, however, generally refers to higher-end switches known as directors. Today's director-class switches contain two types of intelligence: transport intelligence and application intelligence.

Transport intelligence provides enhancements for moving data through the storage fabric while optimizing throughput. The functions mentioned above can be classified as transport intelligence. Such features have been strengthened in the newest directors, which also include a new brand of transportation smarts, such as the ability to handle virtualization and the partitioning of resources.

Application intelligence, on the other hand, provides higher-level storage services, such as storage virtualization, continuous data protection, and backup and recovery.

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