Just out of curiosity John, are you allowed to give us some hints about what your system does? If you are posting on the CentOS list i presume you are running CentOS, rather than "a similar upstream product". Also I'd love to know what you mean by "you do NOT want to have a single 10TB volume" - are you referring to performance or single-point-of-failure issues?
we're drifting pretty far off topic for this list, I was going to let this thread drop... but...
I work for a big 'widget' maker. we develop and pilot our complex little 'widgets' in the states, then volume production is done in our large scale plants overseas. my department is the core development group for the both the core database and the middleware used in our inhouse process tracking system.
I use centos in my groups development lab, mostly for prototyping our messaging/middleware servers... We've validated our databases on rhel/centos, and smaller design center operations who don't need the big sun/emc approach are starting to deploy with oracle on rhel on opteron servers instead of the traditional Solaris/Sun platforms.
re: single 10TB volume, I think its both too many eggs in one basket and performance. I'm not in operations, I'm the systems guy in the development group, so alot of what is decided in production I hear only 2nd hand. I've been told that the big SANs they use don't do as well with very large volume groups as they do with more smaller ones... at the big sites, the SAN is like ~1000 72GB 15K rpm fc drives. I believe Operations uses Veritas VxVM & VxFS on the big Suns (E20k, etc), and it may have performance issues with multiterabyte single file systems, too. Our databases do a LOT of disk writes from synchronous commits, much of the reads are cached (these servers have a LOT of ram). The way our database is organized, there's a nested set of tablespace groups that specific tables are bucketed in, so we can run quite nicely with 3 raids on a smaller system, and 36 raids on a really big system, this makes the space allocation fairly flexible, yet avoids spindle collisions during commonly used complex joins and so forth..