On Wed, Feb 01, 2006 at 01:51:06PM -0800, Carter K. George wrote:
Yes, but all of the NAS vendors have some sort of block storage (or SAN) on the back end. NetApps uses Fibre Channel arbitrated loop "SAN's" for the block access that their file system needs to access storage. So I don't ever think of this whole SAN versus NAS thing as relevant. You always have both file and block access needs. In the simplest case, NAS is the front end and SAN is the back end (and may be effectively hidden, as with NetApps), but there's no case where there's not some sort of block access going on behind a NAS.
I think you are misguided.
To say there is no distiction between 2 competing technolgies because somewhere underneath they do something the same way is not sensible. I could dream up zillions of analogies, but one that may fit this case best is to say that there is no worhtwhile distiction between disk and tape. They both move magnetic media around under a head and read off a block of data. But thats not interesting when making a choice between whether to use a disk or a tape. The important thing is the attributes and cost of each technology as seen from the person (or system) using it.
And the salient distiction between SAN and NAS as stated before is that in one case the system sees blocks, talks via a block access protocol and runs its own filesystem, and in the other case the system sees files, and accesses the files via a file access protocol. The most important point is where the intelligence if the file system resides. With netapp, I get WAFL file system technology, for a SUN and SAN, I get UFS (maybe ZFS) technology.
I know which one I want.
Regards, pdg
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