Will server virtualization end the FC-iSCSI debate?

There are pros and cons on both sides of the argument -- and the winning answer depends on your enterprise's storage strategy

Let’s take a trip to the future this week. Imagine that we travel forward in time -- say, 100 years from now. How will the technological landscape of storage change in one century? What will our descendants think of the state of our technology?

[ MarioApicella's column is now a blog! Get the latest storage news from the Storage Adviser blog. ]

My guess -- perhaps even my hope -- is that our great-grandchildren will look back at our potpourri of conflicting storage technologies and products and cringe. "How could those people ever get anything working out of that spaghetti-like mess?" our posterity might ask.

I am on this train of thought because a recent announcement involving FCoE (Fibre Channel over Ethernet, which I explained in this column a few weeks ago) added another noodle to the dish of storage-tech spaghetti and revived the old FC-versus-iSCSI debate.

That debate (it’s open-ended, but you can find an interesting part of the discussion here) centers around which of the two transport protocols serves better the needs of enterprise storage. It’s a fascinating discussion, and one that triggers pointed and accurate technical comments to support either side of the issue, as they say in Washington, D.C., but unfortunately is also as useless as many political debates.

Why? Because even if one side could prove its point -- and I don’t think either can -- customers don’t necessarily buy the best overall technology. They buy whatever best serves their needs, and the technical excellence argument rarely sways that decision process.

Back to our two transport protocols. Both FC and iSCSI have many appealing points; the former is field-proven and mature, while the latter claims ease of use and a better future (up to 100G). There is obviously more to both technologies than that succinct comparison, but a conversation I had last week with Dell Storage Technologist Matt Baker reminded me of another selling point that iSCSI storage solutions can claim over rival FC-based products. It has to do with server virtualization and how its requirements may impact your storage acquisitions.

“One of the areas that not very many people talk about is storage for server virtualization,” Baker says, adding that many Dell customers are concerned about the intersection points of server virtualization and storage area networks. “Part of what we found [in our customers’ concerns] is the complexity associated with managing a FC-based shared storage solution in a virtual environment."

Baker enumerates the major challenges that admins face when combining server virtualization and SANs, including facilitating VM mobility while maintaining data integrity and data security. What's the best way to back up data, and how can you take advantage of the benefits of a SAN in a virtualized world? 

“As we dug more into it, we started to discover that iSCSI, in many ways, helps to alleviate those challenges,” Baker says. 

From a storage network admin point of view, I couldn’t agree more. For example, Baker referred specifically to VMware, where iSCSI makes it possible to maintain the same touch points that you have in a real environment unchanged in a virtual machine. That includes the initiator-target link, running backups in the same machine, moving the guest environment to a different VM, or moving a VM to a different ESX server.

By contrast, to do the same things with an FC SAN you need to touch the storage network at several points, which may include an FC switch and one or more HBAs. Also, in a VMware ESX environment, the Hypervisor -- not the VM -- owns the HBAs, which means changing things sensibly. Ditto if you want to move back to a physical machine.

Is that a big deal? Probably not, as skilled admins can do that in minutes and with a hand tied behind their back, but it still takes some time. Moreover, depending on who calls the shots in your datacenter, letting the VMware admin manage VM related-storage (as you are forced to do with FC) could be an improvement rather than an obstacle. You may want to read what they say about this on the IT 2.0 blog.

So there you have it: Server virtualization is a double-edged sword that can cut on both the iSCSI and the FC side. Our great-grandchildren might still be debating which one is best 100 years from now.

Join me on The Storage Network with questions or comments.

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