How to choose a SAN switch for SMBs

Storage environments in SMBs can range from a few servers and a couple of terabytes, to hundreds of servers and hundreds of terabytes. In this tip, Greg Schulz discusses some of the features to look for in a SAN switch in iSCSI, FCl, FCoE or InfiniBand-based SANs environments.

Storage environments in small to midsized businesses (SMBs) can range from a few servers and a couple of terabytes, to hundreds of servers and hundreds of terabytes. Entry-level storage area networks (SANs) can be built using iSCSI and general-purpose Ethernet technology.

Larger storage environments can leverage Fibre Channel. Or, in the future, they can use Fibre Channel over Ethernet (FCoE), combined with Data Center Ethernet (DCE), which is what Cisco Systems calls premium, low-latency, lossless Converged Enhanced Ethernet (CEE).

With all of these options, what are some other features to look for in a SAN switch, regardless of if it is for iSCSI, FCl, FCoE or even InfiniBand-based SANs for SMB environments?

Scalability

Scalability means many different things, from performance to availability to the number and type of ports and protocols supported. For example, Ethernet switches can have 10/100 Mb, 1 GbE or 10 GbE ports. They can be fixed or flexible to use different types of transceivers, including copper or optical, as well as uplink ports for attachment to backbone network switches. In a Fibre Channel SAN environment, this would be called a trunk or Inter-Switch Link (ISL). For Fibre Channel switches, the ports most likely will be 2 Gb, 4 Gb or 8 Gb.

Reliability, availability and serviceability

Things to look for in a SAN switch include redundant power supplies and cooling fans for applications where high availability is required. You also want to be able to update firmware or software on-the-fly (non-disruptive code load), as well as the ability to activate those changes on-the-fly (non-disruptive code activation).

For larger SAN switches, modularity can mean the ability to add new switch blades or line cards with more ports either disruptively or non-disruptively for expansion purposes. Management tools, including diagnostics and interfaces with popular SNMP or SMI-S protocols, help with problem notification, determination and resolution.

SAN switch security and management tools

From a management and security standpoint, items to look for when considering different SAN switches for SMB environments include ease-of-use features such as non-disruptive upgrades of software or maintenance updates, as well as integration with existing management tools.

Security tools and features to look for include integration with RADIUS for authentication of management functions, as well as for access to secured switch ports. Another item to look for is N_Port ID virtualization support, which is useful in VMware and other server consolidation environments to create a unique Fibre Channel World Wide Port Name (WWPN) on a shared physical adapter.

Packaging

There are many different packaging, associated pricing and physical environmental considerations for SAN switches. There are desktop and rackmount switches, as well as blade switches. What type of packaging is best depends on your needs and other requirements.

SAN switch pricing

Trying to compare switches on a price-per-port basis can lead to an Advil-sized headache, given the various types of ports, copper, optical, long range or short range, speed and functionality, performance, and packaging. Some switches will be more expensive on a per-port basis based on performance, protocols and other features. For example, not surprisingly, a 1 GbE switch should be much cheaper on a per-port basis than 4 Gb or 8 Gb Fibre Channel switch, as well as a 10 GbE switch, however, the performance per port will also differ.

Ethernet ports are generally seen as less expensive than Fibre Channel ports; there are some surprises between 8 Gb Fibre Channel and 10 GbE. For example, Hewlett-Packard has a starter kit that contains four 8 Gb Fibre Channel PCIe adapters, optical transceivers, cabling and an eight-port 8 Gb Fibre Channel switch. This kits costs less than $9,000, whereas 10 GbE single-port adapters with optical transceivers are in the $800 to $1,000 range at venues like CDW.

About this author: Greg Schulz is founder of the StorageIO Group and author of the books "Resilient Storage Networks — Designing Flexible Scalable Data Infrastructures" and "The Green and Virtual Data Center".

For more information about SAN switches, read Chapters 4, 5, 6 and 9 of "Resilient Storage Networks – Designing Flexible Scalable Data Infrastructures," as well as Chapter 9 of "The Green and Virtual Data Center."


This was first published in November 2008
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