Recent words from Steve D.,
Forget NAS and SAN, Its USN Now
By Steve Duplessie
The original terms no longer make sense. I propose a new term, Ubiquitous Storage Networks. I don't think I can make money on the term, so I offer it freely. Why do we need yet another storage acronym? Quite simply, because the old ones no longer apply to the world in which we now live.
Storage Area Networks (SAN) has been the acronym of the last few years. It implies fibre channel connected servers and storage, but need not be fibre exclusively (Escon or SCSI are also viable SAN connects). What everyone did agree on was that SAN was a "block data" infrastructure. This means that a host (server) will access a disk device and read/write blocks of data, using the SCSI driver in the operating system, just like it always has. A multitude of these servers (in theory) could be connected to common, shared storage arrays - each with a very high-speed bus, via an elaborate switched architecture. Each server (in theory - note the theme here) would think it had its own direct attached storage, and not worry about anybody else messing with its data. We like the SAN concept (and still do) for these reasons:
With insane on-line growth requirements, being able to centralize storage physically is a good idea.
Downtime will be reduced with centralized storage architecture.
We can manage much more storage with much less people in a centralized configuration.
We can add physical storage, or additional servers, onto the SAN while it remains running.
Now we've all heard about how SAN has not lived up to its promise - about all the interoperability issues, etc. That is changing, by the way, and soon you will get the utopian SAN solution you were told about years ago. That's not my point, however.
NAS, or network-attached storage, has been around for a long time. You pre-acronym old-timers might remember calling it "file serving". Basically, NAS is implemented by taking the same disks as in SAN, but putting them behind a file server engine, and attaching that engine to your standard, run of the mill, Ethernet network. Think of NAS as a SAN (using Ethernet instead of fibre channel) whereby servers (or clients) request data in File Format, not as raw blocks.
There has always been tremendous debate about which is better, SAN vs. NAS. SAN is fast but expensive and has interoperability problems, NAS is easy, cheap, and has no interoperability problems, but is slow, etc. etc. (hey, look, I didn't invent the arguments, I'm just writing what the world thinks). Blah, blah, blah.
The reason neither acronym works any longer is this whole iSCSI phenomenon (storage over IP). We will soon be able to use common networks to move either block or file data. It may be IP, Infinband, or Fibre Channel. So, a Storage Area Network may well be based on Ethernet and allow us to support concurrent file and block based requirements. Hence, Ubiquitous Storage Networks (by all means, come up with a better acronym, you won't hurt my feelings). The point is that we won't be able to use traditional definitions much longer.
The bad news is many of you still don't understand what the heck anyone is talking about when they say SAN or NAS, and now I'm complicating things even more. I would call it Storage Networks, but my friends in Waltham, MA might take exception. The good news is where there is confusion, there is always a vendor or two ready to take advantage. That keeps us in business.
This is not the forum to debate the technical merits, or lack thereof, of each of the USN methodologies. There will be plenty of time for that. All I'm suggesting is that you best start thinking about acronyms. Matter of fact, send me your ideas and we'll all work together to pick a winner. It's about time users got to create their own acronyms, I mean, why let the marketing guys get all the glory?
Steve Duplessie is the founder and Sr. Analyst at the Enterprise Storage Group of Milford, MA. The Enterprise Storage Group is the leading storage specific analyst firm. Steve can be reached at steved@enterprisestoragegroup.com.
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