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iSCSI and NAS performance issues

Where do companies see the benefits of the emerging iSCSI standard, as a TCP offload engine (TOE) or as an alternative to NAS? Are companies deploying any iSCSI solutions and if so, on what platforms?

You've confused a few things here. The iSCSI standard basically has nothing to do with TCP/IP acceleration commonly called TCP/IP offload engines. That is done by separate hardware (processing and buffers) on the host bus adapter (on NIC if you prefer) to move some of the overhead that was done by the server/client processor into another, more specialized processing element. This can greatly improve networking for NAS as well as iSCSI.

Many of the vendors for these TOEs have also included the session layer controls (at least to some extent) for iSCSI on the same HBAs (or NICs) with the idea to speed up iSCSI because of the amount of overhead that is being added. That is probably a requirement to reach an acceptable level of performance for many customers, but not all. So that means a new HBA (NIC) and new device driver for it because the implementations by different vendors vary quite a bit so there will be different drivers.

There is not much deployment of iSCSI yet but there are quite a few products that have been made available. Most people expect iSCSI to be in the small- to mid-size business market and will indeed compete with NAS solutions. The NAS solutions will be simpler and much quicker to implement and administer. The most likely early successes for iSCSI will be in Windows environments for Exchange that is not recommended for NAS devices and other applications that may not be recommended on NAS.

It will be a tough choice for many because it requires understanding the application, the needs of the organization and the amount of administration and support required. There's also a lot of confusing (and reprehensible) hype from companies that just is outrageous. Again, make an informed decision and stay out of religious zealot discussions.

Randy Kerns
Evaluator Group, Inc.


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