NetApp filer is fully supported for use with MS Exchange. I don't see how this could lead to a problem more than any direct-attaced storage.
NetApp choking on lots of small files? I don't think so. WAFL handles small files far better than most file systems notably UFS.
Great. That's why I mentioned it, but the netapp of a few years ago wasnt the same, or so Ive come to believe.
Waste of space? Maybe. NetApp uses 4K blocks so if you have lots of really small files <4K then you'll waste quite a bit of space.
The average usenet article is under 64KB. 4K is about the average size of an email, including headers.
As far as using it for Exchange, *I* would, but that's me. Generally, Microsoft and NFS don't mix well, even though they give lots of lip service to it.
-M