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VM & iSCSI

1:30 PM -- We've been doing a lot of research and testing around VMware storage protocols lately, and I am coming to the conclusion that among the big three -- Fibre Channel, iSCSI, and NAS (NFS) -- iSCSI is the odd man out. I'm going to spend the next two or three blogs sharing my thoughts on what we are seeing, and I'm looking forward to some feedback.

First, I know that getting into protocol discussions is about as safe as getting into de-duplication discussions, but let me state my case. If you are making a selection today, your choices are typically going to be 8-Gbyte FC (maybe 4-Gbyte), 1-Gbyte iSCSI, and 1-Gbit/s or possibly 10-Gbit/s Ethernet with NFS.

When it comes to building a VMware storage infrastructure, the decision points often seem to come down to performance, cost, and ease of use. Sure, there are other issues like security and reliability. But most customers focus on the former three. There is also the comfort factor -- you are most likely to use what you use now or what your peers use.

When it comes to straight performance, most people will concede that Fibre has the performance advantage from a raw numbers standpoint, and, if your hosts and associated workloads can actually take advantage that type of performance, then Fibre is the most likely candidate. For some customers the performance capabilities of iSCSI and NFS are acceptable, especially initially.

If your I/O performance can be easily sustained by either iSCSI or NFS, then you are looking at ease of use and costs, as the two protocols are virtually tied in storage I/O performance. For many, iSCSI used to be the "go to" technology for ease of use. The basic concept was that it ran over IP so it had to be easier. I've been working with iSCSI since 2002, and it has always been pretty straightforward, especially if the customer can get away with using software initiators, and the performance of a standard Ethernet card is acceptable to them.

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