SAN management user case study, part 3

The third installment in our 4-part series, written by members of the wikibon.org community, focuses on the need for end-to-end SAN monitoring tools for large, heterogeneous storage networks.

Turn on the lights: What you need to know about the dark art of SAN management

By John T. McArthur, Wikibon.org

-- Because of the limited adoption of storage area network (SAN) monitoring and reporting tools, storage capacity and performance management has, for years, been a dark art. As a result, when storage administrators say to their CIOs that they "need more storage for the SAN," they could be proposing a solution to a problem that, at best, they do not fully understand and, at worst, may waste money and fail to meet the performance needs of the application owners.

A SAN is more than the amount of data the SAN can hold. A SAN includes storage, switches, and adapters. In addition, each component comes with a host of configuration options, which may impact performance and available capacity. In order to ensure that data is delivered to applications when needed, storage administrators need tools to monitor, track, and forecast key metrics of storage capacity and SAN performance.

A SAN is a system. If a SAN were a transportation system, the storage might be the passenger bus. A bus holds a certain known capacity, has the potential to travel at a known maximum speed, can be boarded (filled up) and exited (emptied) at a known rate. The job of the bus is to get people and packages from location A to location B on time, without losing them or damaging them. And when the bus is full, it's full. If in a given amount of time you have more people to move than the bus can hold, you will need another bus. But the ability of the bus to perform the people-delivery service is also dependent upon the health of the bus, the quality of the roads, the speed limit, the amount of traffic on the road, and the optional routes, should the normal route become unexpectedly congested.

So how do transportation administrators know when they need more buses? Unfortunately, a picture of a full bus tells a transportation director very little about the ability or inability of the transportation system to deliver passengers on time and whether more buses are needed. The same holds true for SAN administration. A picture of a full storage system tells the CIO and the storage administrator very little about the ability of the SAN to meet the needs of the applications it supports.

Much has been made of the exponential growth of storage, but Ryan Perkowski, a SAN manager at a major U.S. credit card company, found through SAN monitoring and reporting tools that his company's capacity requirements were actually growing on a linear basis, not exponentially. At the same time, I/Os per second (IOPS) were, in fact, growing exponentially. The information contained in his Virtual Instruments NetWisdom reports helped his company avoid over-provisioning of storage capacity, and enabled him to focus instead on providing the required storage performance and capacity.

Just as importantly, the historical reports on performance trends enabled Perkowski’s company to identify impending performance bottlenecks and prevent them. The point-in-time capacity and performance snapshots that are the limit of many storage and switch vendors' reporting capabilities are inadequate for intelligent SAN management.

Perkowski explained his SAN management dilemmas and solutions at a recent Wikibon Peer Incite meeting.

The adoption of storage tiers is expanding, and storage administrators are increasingly looking for Tier-0 (solid-state disk, or SSD, drives) to address their performance, not capacity, requirements. Investments in Tier-0 storage are substantially easier to understand and justify when viewed in the context of robust SAN reports of both capacity and performance. But if the real problem is in the network, rather than the storage systems, then that investment may not remedy the problem.

Action Item: CIOs and IT storage managers should place a priority on investments in SAN monitoring and reporting software to enable better SAN management and predictive performance analysis. In times of limited budgets, these investments should have a higher priority than investments in inadequately justified infrastructure. At the same time, CIOs should develop a richer shared vocabulary with their storage administrators to better describe, understand, and justify future investments in storage systems and storage network infrastructure.

Virtual Instruments' NetWisdom is one of the reporting tools used by Perkowski. Virtual Instruments' tools are targeted at meeting the SAN monitoring and reporting needs for large, mission-critical, heterogeneous SANs. Perkowski also uses NetApp’s SANscreen SAN management software.

John T. McArthur is a Wikibon.org member.

Related articles:
SAN management user case study, part 1: Opening Pandora’s box of SAN management
SAN management user case study, part 2: Pay for performance: Justifying SAN performance tools

This article was originally published on January 29, 2010