By creating a separate, high-speed network to connect storage devices with each other and with multiple servers over a switch fabric, storage networking provides access to data sources which is more robust, more flexible and more economic than conventional directly attached storage (DAS). Storage networks are an essential foundation for modern information management systems. But even without complementary virtualisation and information lifecycle management technology, their often high set-up costs can be recouped by savings on equipment and administration.
A key driver for investments in storage networking – and particularly storage area networks (SANs) – is the wider need to consolidate servers and increase the utilisation of server and storage resources. The nature of DAS is such that most organisations have tended to buy disks on a peak-demand, just-in-case basis. Typical DAS installations often only utilise 30% or less of their disk capacity. By allowing servers to share disks across a SAN, utilisation rates can be pushed above 80%.
SANs have other benefits. Although installing and managing them is a highly skilled occupation, administrators can manage two or three times as much storage capacity than they could in a DAS environment. And, since SANs separate storage from processors, management can be conducted with minimal disruption to ongoing production operations.
Another key benefit of storage networking is the ability to mix different kinds of storage resources across the network, and to allow storage devices to communicate directly with each other without siphoning off server capacity that would otherwise be used to drive applications. Disk arrays, for instance, can be configured to conduct their own back-up routines with shared tape libraries – increasing tape utilisation and minimising disruption caused by back-up or archiving compared with DAS systems.
Essentially, storage networks create a separate world for data which protects it from the vicissitudes of the world of processing, and vice versa. This has benefits for both sides. In typical DAS environments, 30% or more of systems downtime is routinely attributable to disk failures, but with fewer single points of failure in a SAN environment storage-derived system, failure can be greatly reduced.
For these reasons alone, most large organisations and – as SAN technology becomes cheaper – many medium-sized organisations have already found compelling reasons for investing in networked storage technology. However, creating a storage network is only a first step.
Today, a growing number of organisations are embarking on the next phase of data storage management, and investing in storage virtualisation technology.