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Choosing a Fibre Channel array or iSCSI SAN storage for SMBs

Choosing a Fibre Channel array over an iSCSI storage system SAN requires resellers and customers to carefully compare the storage area network technologies. This tip discusses iSCSI and Fibre Channel side by side.

The recent maturity of products for the iSCSI market has provided IT channel professionals with the option of offering their customers more than one flavor of storage area network (SAN). So how should you decide if Fibre Channel (FC) or iSCSI is right for your customers?

Fibre Channel background

More on iSCSI and FC SANs
iSCSI SAN or Fibre Channel SAN for SMBs

iSCSI SANs vs Fibre channel SANs in SMBs

Fibre Channel was developed in the late 1980s and ratified as an American National Standards Institute (ANSI) standard in 1994. It is now a mature technology that provides a high-performance, high-speed switched storage network using dedicated host, switch and storage hardware. Fibre Channel SANs were introduced to improve connectivity between storage and hosts, consolidate storage systems and improve performance.

iSCSI background

iSCSI, only ratified in 2003 by the Internet Engineering Taskforce (IETF), is a low cost IP-based protocol for connecting storage and hosts using existing or dedicated IP networks. iSCSI was developed to address the need for a more cost-effective alternative to Fibre Channel; IP networking technology is inherently cheaper than Fibre Channel (more later). Both iSCSI and Fibre Channel connect host and storage using the standard SCSI command set and therefore provide block-level access to data.

Determine SAN requirements

Before offering any solution, ask your customer what it is they require.

  • Availability: What level of availability is required for the SAN? Is it critical that the SAN be available at all times, or is downtime for maintenance or equipment failure tolerable?
  • Performance: What level of performance is required from the SAN? Is data throughput by the host an important factor? Is total throughput of the SAN an important factor?
  • Applicability: What type of data is the SAN being used for? Is it mission-critical production data or a development environment?

Match requirements to SAN constraints

Once requirements are understood, these should be matched to the constraints of each technology type.

  • Cost of equipment
    Fibre Channel: FC equipment is considerably more expensive than iSCSI. Host bus adapters (HBAs) can cost approximately $500 to $1,000 each. Fibre Channel switches (or directors for higher availability) cost around $1,000 per port connection.
    iSCSI: iSCSI can use standard Ethernet network adaptors and IP switches of much lower cost.
  • Cost of management
    Fibre Channel: FC SANs cost more to administer than iSCSI SANs. There is a higher cost for management software; skilled FC SAN professionals are expensive to recruit and train.
    iSCSI: iSCSI uses standard networking technology and can be implemented by IT professionals within an organization who are already familiar with IP protocols.
  • Reliability
    Fibre Channel: FC has a proven record in reliability. FC switches are engineered for high availability (director-class switches offer 99.999% availability) and vendors perform extensive testing to provide certification of HBA, switch and storage array products. In addition, Fibre Channel drivers and support for additional recovery and reliability features such as multipathing is well established.
    iSCSI: iSCSI can be implemented across standard network technology and the vendor certification process is not as rigorous; it is therefore less reliable than Fibre Channel when considered for mission-critical applications.
  • Platform support
    Fibre Channel: FC is supported across a wide range of operating systems and applications.
    iSCSI: iSCSI currently has narrower support by platform. For instance, only Sun Solaris 10 onward supports iSCSI natively.

Choose a SAN solution

It isn't possible to say exactly which SAN type will meet each customer requirements as needs will differ subtly from customer to customer. However, here are a few general guidelines to make the decision easier.

  • Consider choosing Fibre Channel over iSCSI for SANs where availability, performance and reliability are paramount. For example, a SAN supporting a mission-critical transaction processing system will be more suited to Fibre Channel.

  • Consider choosing iSCSI where acceptable compromise and tradeoffs can be made or are required to meet the customers needs. For example, an iSCSI SAN may be suited to the customer who may not be willing to invest in acquiring or training staff to support Fibre Channel.

    About the author: Chris M. Evans is an independent storage consultant with Brookend Ltd., with nearly 20 years' experience in a wide range of storage platforms covering mainframe, open systems and Windows. Chris specializes in network-attached storage (NAS) and storage area network (SAN) technologies, designing and implementing large-scale infrastructure projects for major financial corporations. Online, Chris maintains www.storagewiki.com; you can catch up with him on his blog at www.storagegurus.com.

  • This was last published in January 2007

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