Interview

“VSANs build a lot more intelligence into the network”

Technology progression is the new order of the day. Even before you think of it, tech pioneers have it for you. Idris T Vasi, director, Asia Pacific, Optical Storage Networking, Cisco Systems explains how virtual storage area networks (VSAN) actually work in an interview with Rahul Neel Mani

* What is the concept of virtual storage area networks (VSANs)?

Today, SAN designers build separate fabrics, otherwise known as SAN islands, for a variety of reasons. A SAN island refers to a completely physically isolated switch or group of switches used to connect hosts to storage devices. The reasons for building SAN islands can be the desire to isolate different applications into their own fabric or to raise availability by minimising the impact of fabric-wide disruptive events. In addition, physically separate SAN islands also offer a higher degree of security as each physical infrastructure contains its own separate set of fabric services and management access. While these are valid reasons for building separate fabrics, this practice can quickly become costly and wasteful in terms of fabric ports and resources.

To help achieve the same isolated environments while eliminating the added expense of building physically separate fabrics, Virtual SANs offer the ability to scale SANs beyond current limitations in a resilient, secure, cost-effective, and manageable fashion.

* How different are VSANs from conventional appliance-based SANs?

A VSAN provides the ability to create separate virtual fabrics on top of the same redundant physical infrastructure. The prospect of additional separate fabrics—that SAN propounds—means more hardware, more ports, more cost, more devices to manage, and typically, underutilised hardware. If one fabric has many unused ports and another fabric is short of ports, one cannot simply reassign the unused ports where they are required. VSANs are able to deliver all these benefits to enterprises. The bottom line: VSANs build lot more intelligence into the network and make it possible for enterprises to run value-added services.

l What gains can a storage administrator or a storage manager get through VSANs?

Using VSANs, SAN designers can raise the efficiency of a SAN fabric and alleviate the need to build multiple physically isolated fabrics to meet organisational or application needs. Instead, fewer, cheaper redundant fabrics can be built, each housing multiple applications, and still providing an island-like isolation. Spare ports within the fabric can be quickly and non-disruptively assigned to existing VSANs, thereby providing a clean method of growing application-specific SAN islands virtually. Another major benefit of the VSAN feature is in terms of its contribution to high availability. VSANs provide not only hardware-based isolation, but also a full replicated set of Fibre Channel services for each VSAN.

* What intelligence do VSANs bring to the SAN environment?

VSAN technology partitions a single physical SAN into multiple VSANs. Each VSAN is a logically and functionally separate SAN with its own set of fabric services. This partitioning of fabric services greatly reduces network instability by containing fabric reconfigurations and error conditions within an individual VSAN. VSANs provide strict traffic segregation to help ensure that the control and data traffic of a given VSAN is confined within its own domain, increasing SAN security.

Users can create administrator roles that are limited in scope to certain VSANs. For example, a network administrator’s role can be set up to allow configuration of all platform-specific capabilities, while VSAN administrator roles can be set up to only allow configuration and management of specific VSANs.

* How do VSANs offer data traffic segregation?

Routing and forwarding tables are downloaded to the Fibre Channel switching modules from the supervisory module, so that data traffic switching can be done at wire-rate while maintaining data traffic segregation between VSANs.

* How do VSANs help in management and reducing overall storage deployment costs?

VSANs, today offer the SAN designer a more cost-effective and reliable SAN deployment. Among the biggest advantages of a VSAN is that it enhances fabric scalability and availability, and further augments the security services offered by existing storage technologies such as fabric zoning and SAN. VSANs, combined with hardware-enforced zoning, provide the SAN designer with new tools to highly optimise SAN deployments in terms of scalability, availability, security and management.

VSANs provide the ability to create completely isolated fabric topologies, each with its own set of fabric services, on top of a scalable common physical infrastructure.