Storage Area Network Information Center

An inventory and analysis of your current environment will help you determine which, if any, hosts and storage devices from your existing storage infrastructure you would like to re-deploy in your Storage Area Network (SAN), and what physical environment requirements will affect your choice of new components. Once you've done this, you can form your total SAN solution by:

• Determining which new components are needed
• Validating compatibility across your new and existing components
• Calculating the number of switch ports needed to interconnect all hosts and devices

You can use SAN Components Inventory Worksheets (XLS) to record your new component selections. You may have already started filling these worksheets out in the previous step.

SELECT YOUR COMPONENTS

Need a refresher course on SAN components?

Fibre Channel Switches (SAN Fabric)

Since switches form the intelligent foundation of your SAN, it's important to select the right ones for your business requirements. Consider the following:

Hardware Redundancy:An option on switches is a dual, hot-swappable power supply and hot-swappable cooling fans to ensure optimal uptime.

Port Count: Switch productlines should offer a wide range of port count choices from entry-level (8-16 ports) to enterprise-level (64-128 ports) to best meet changing business requirements. You can use switches alone, or link them to form a network of larger port-count fabrics. The number of ports you need will depend on your choice of single or dual-attached hosts and storage devices.

Management and Monitoring Software: Switches should offer a wide variety of easy-to-use, Web-based management and monitoring tools to meet a variety of needs.

Security and Access Control Software: Switches should offer software that protects your SAN from security breaches as well as software that enables secure sharing of storage resources accross your SAN.

Integration with Third-Party Applications: For your SAN to be able to tie into existing management infrastructures and SAN management tool sets, the switches should offer an application programming interface (API) that third-party vendors can use to integrate their products with your switch software and hardware.

Speed: Switches are available today that support both 1 Gbit/sec and 2 Gbit/sec throughput per port. Many offer auto-sensing and speed-matching capabilities for both existing and next-generation devices.

Budget: Balance your budget realities with your needs. Remember that with SANs you can easily "pay-as-you-grow," so purchase the best features you can afford now and expand when your business demands it.

Standards Involvement: Be certain switches adhere to industry standards and that the manufacturer is actively involved in standards bodies to promote interoperability, and provide customers with investment protection and flexibility to choose best-in-class SAN components.

Forward and Backward Compatibility: Switches should be forward and backward compatible with other switches in the product line so you can migrate from 1 Gbit/sec to 2 Gbit/sec SAN environments and deploy a highly scalable core-to-edge storage networking infrastructure.

Storage Devices

There are many types of disk and tape storage devices available that meet a wide variety of storage requirements. Make sure the devices are Fibre Channel ready. Integrating a variety of devices into your SAN allows you to allocate storage based upon cost, availability, and performance criteria. If critical application data is stored on a device, you'll want to have that device dual-attached to your fabric to ensure high availability. That requires double the number of Fibre Channel connections on that device.

Host Bus Adapters (HBAs)

The requirements of the applications that will run on your SAN should help drive what type of HBAs you need on your hosts. From the available 1 Gbit/sec, 2 Gbit/sec, and auto-sensing speeds, choose the speed needed to match your current and future data throughput requirements. If critical applications are running on a host, you'll want to have that host dual-attached to your fabric to ensure high availability. That requires double the number of HBAs for that host.

Cabling

Copper and optical are the two primary types of media used for the physical cabling between the components of your SAN. While copper is less expensive, optical provides a reliable signal over a longer distance. Copper has distance limitations such that it is typically only used within a rack. The type of connections made within your SAN will often be driven by your device connection needs.

		Cost		Optimal Distance (meters)
Copper (STP)		$		< 25
Multimode Optical		$$		2 - 500
Single-mode Optical		$$$		2 - 10,000

		Cost		Optimal Distance (meters)
Multimode Optical		$$		2 - 300
Single-mode Optical		$$$		2 - 5,000

Cable Connectors

Gigabit Interface Converters (GBICs)

• 1 Gbit/sec: short-wave (500 meters) or long-wave (10,000 meters)
• 2 Gbit/sec: short-wave (300 meters) or long wave (5,000 meters)

VALIDATE COMPATIBILITY

An important step in finalizing your component choices is to validate compatibility of all components within your SAN. Check compatibility lists provided by SAN vendors. Update your SAN Components Inventory Worksheets to reflect the compatibility status.

CALCUATE YOUR NEEDED PORT COUNT

• Number of HBAs on your hosts
• Number of Fibre Channel connections on your storage devices

Remember that if you want dual-attached hosts and devices to ensure high availability, you need to double your port count for those hosts and devices. Also, if you need the highest uptime possible, implementing dual fabrics is additionally recommended. The next step will cover dual fabrics and availability in more detail. Update your SAN Components Inventory Worksheets to reflect any changes in port count.

Previous: Inventory and Analyze Your Environment