How to compare Fibre Channel (FC) and SCSI

What you will learn from this tip: Things to consider when comparing FC and SCSI technology.

A SearchStorage.com reader recently asked:

How do you compare SCSI based storage technology with Fibre Channel based, and how do you compare them if the storage size is maximum 2 terabytes (TB)?

Two important steps to compare different technologies, in this case

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SCSI and Fibre Channel (FC) based storage, is to understand the applicable technology and your requirements. Understanding your requirements will help you determine which differences in the technology are relevant and important to your specific needs. An understanding of the technologies is important to be able to make fair and relative comparisons and avoid making apples to oranges comparisons.

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So, here are a few things to consider and understand. Are you looking at and comparing storage systems with SCSI or Fibre Channel host ports (front-end)? Are you comparing back-end SCSI or FC disk ports and drives? Or, is it a combination? For example, a storage system could have FC host ports, yet utilize SCSI or emerging SAS disk drives.

From a disk drive perspective, FC, SCSI and SAS are about equal in terms of performance, reliability, capacity and features including dual-porting. From a host storage interface, SCSI can be less expensive due to lower costs by eliminating switches and using embedded server or low cost SCSI adapters. FC, on the other hand, provides more flexibility in terms of distance, flexible topologies and number of devices and servers that can be attached. From a performance standpoint, for most applications either SCSI (Ultra160 and Ultra320) or FC should be sufficient. Another alternative for block-based storage access would be to use iSCSI- or a SAS-based controller to attach emerging SAS-based storage to servers.

If your requirements are for 2 TB of storage, clarify whether you are referring to usable or raw capacity. For example, if you need 2 TB of usable storage and plan on using mirroring for data protection, you will need 4 TB of storage plus any applicable spare disk drives. There are many vendors whose products can scale up to 2 TB, or put another way, scale down to 2 TB, including the EMC AX100, HDS WMS100, HP MSA, IBM (DS400, DS300, DS4100, N3700), Sun/STK 3000 series and Xiotech Magnitude 3D 3000e among others.

For more information:

The slow move toward faster Fibre

About the author: Greg Schulz is a senior analyst with the independent storage analysis firm, The Evaluator Group Inc. Greg has 25 years of IT experience as a consultant, end user, storage and storage networking vendor, and industry analyst. In addition, Greg is the author and illustrator of "Resilient Storage Networks". Greg holds both a computer science and software engineering degree from the University of St. Thomas.

This was first published in November 2006

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