Dr. I Doctor
Dr. I Doctor's Informational Juggernaut
August 1, 2008
Choosing Between FC and iSCSI SAN
Dear Doctor,
We're moving to server virtualization and are planning for a Storage Area Network (SAN) array to provide disk storage for all our virtual machines. My problem is choosing between the two SAN technologies, Fibre Channel (FC) and iSCSI. I know iSCSI is newer, but FC is 4 Gbps versus iSCSI's 1 Gbps. FC costs more, but I don't want to saddle our virtualization effort with a slow storage solution unnecessarily. We will be running mission-critical database applications on the SAN, and performance must equal what we see with native hardware. Is there any clear right answer to this question?
Gentle User,
The essence of your question is performance, so the answer depends on the severity of the disk transaction load you want to virtualize. It's true that FC is faster today, but iSCSI's next speed bump is from 1 Gbps to 10 Gbps, more than double the performance of FC. If possible, try testing your application on an iSCSI SAN before deployment. Some iSCSI vendors also have modeling tools that can help you predict performance.
The most expensive aspect of FC is the infrastructure: You must purchase expensive FC Host Bus Adapter (HBA) cards for every virtual host server and interconnect them with pricey, proprietary FC switches. This can double or triple the overall cost of virtualization deployment. iSCSI uses standard off-the-shelf Ethernet equipment that is much less costly. Where necessary, you can augment standard hardware with high-performance iSCSI TCP Offload Engine (TOE) or HBAs to address performance needs on individual servers. If money is no object, FC is the safest solution today.
Posted by mbeckman at August 1, 2008 1:01 AM
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