If you're currently reviewing a customer's storage area network (SAN) design and considering scaling beyond a single...
fabric, there are a variety of technologies and products that can help.
First we'll review reasons why you'd scale out a SAN beyond a single fabric on a local or wide-area basis.
Why scale out a SAN
Understanding your customer's storage networking objectives, along with what level of scalability and resiliency they require, is integral to developing the storage area network design. Attributes and service requirements associated with scaling a storage network include:
Now that you've determined when you'd scale beyond a single fabric, you must decide how you're going to go about accomplishing this goal. Here are your options:
How to scale out a SAN
Key technologies for scaling out a SAN
A key technology for enabling storage networks to span single fabrics and locations is a storage network router. Vendor and marketing hype aside, there are generically three types of functions that storage networking routers perform:
- Segmentation and inter fabric routing (not to be confused with partitioning).
- Protocol conversion (not to be confused with mode conditioners).
- Storage over distance enablement using IP, SONET/SDH and optical networks.
The emergence of SAN segmentation and inter-SAN fabric routing capability is enabling SAN sub networks to be created. For example, if you connect two SAN fabrics together, they will be merged into a single fabric. The result will be a combined SAN fabric that could have device and address conflicts and a proliferation of state change and management traffic across both networks. Segmentation also can be used to isolate management traffic from different fabrics and keep traffic local. Some products only support a single function such as protocol conversion or distance enablement. Other products support two or more functions and others from vendors including Brocade (Multi-Protocol Router), Cisco (MDS 9216i) and McData (Eclipse) support all three basic routing functions.
The following table shows technologies that can be used to support different storage functions for scaling on a local and remote basis, for example using iSCSI and FCP for block storage access and NAS for file-based access. Not shown in the table below are vendor-unique technologies that support such functions as segmentation and partitioning.
|Storage Network Scaling Technologies|
|Block Storage Access||No||Yes||No||Yes||No|
|File Storage Access||No||No||No||No||Yes|
|Storage over Distance||Yes||Yes||Yes||Yes||Yes|
|SAN Fabric Segmentation||No||No||Yes||No||No|
|Tunneling Fibre Channel||Yes||No||No||No||No|
About the author: Greg Schulz is founder and senior analyst of The StorageIO Group in Stillwater, Minn., and author of the book Resilient Storage Networks (Elsevier).