(I'm curious because I run an HPC installation with Lustre and NFS over XFS, and trying to think of the future. MBTF doesn't matter as much as raw speed while it actually runs.)
Lustre, as truly awful as it is, is a POSIX filesystem (or close enough for (literally) government work).
Redhat/Ceph only at the end of April, announced that POSIX functionality was ready for production. Personally, that's not when I'd choose to deploy production storage. Ceph object and nominally block have much more time in production.
If you need POSIX, trusting Ceph at this point is an issue unless, as you say, MTBF isn't a concern. You might want to try BeeGFS, a similar logical model but much simpler to implement, performance up to a very high level, and a record of reliable HPC deployments (as oxymoronic as that sounds).
If you can do with object then certainly exorcise Lustre from your environment in favor of Ceph (or try Scality if non-OS isn't an issue). Lustre's only useful as a jobs program anyway - keeping people occupied who'd otherwise be bodging up real software.
As someone who completely shares your Lustre sentiment, I can't fathom why Intel keeps pouring resources into it.
The problem (surprise!) is IBM. It's mature software, which means 21st Century Desperate IBM sees it as a cash cow - aggressively squeezing customers - and as something they can let their senior, expensive developers move on from - or lay them off in favor of "rightsourcing". You can certainly trust your data to it (unlike Lustre), but it'll be very expensive, especially on an ongoing basis, and the support team isn't going to know more than you by then. Also expect surprise visits from IBM licensing ninja squads looking for violations of the complex terms, which they will find.
As for Lustre, it brings to mind Oliver Wendell Holmes, Jr's, "Three generations of imbeciles are enough". I've been at least peripherally involved with it since 1999, with LLNL trying to strong-arm storage vendors into support. Someone should write a book following 16 years of the tangled Lustre trail from LLNL/CMU/CFS -> Sun -> Oracle -> WhamCloud -> OpenSFS -> ClusterStor -> Xyratex -> Seagate -> Intel (and probably ISIS too).
The answer to your question IHMO, is that Intel just isn't that smart. They're basically a PR firm with a good fab in the basement. What do they know about storage or so many other things? People don't remember when they tried to corner the web serving market back during the 1st Internet boom. They fail a lot, but until now had enough of a cash torrent coming that it didn't matter. They still do, of course, but there are inklings of an ebb.
Typical IBM, though. (shakes head)
https://www.mellanox.com/related-docs/solutions/ppt_ceph_mel...
http://www.snia.org/sites/default/files/JohnKim_CephWithHigh...
Also, look at Sector/Sphere which was made by UDT designer for distributed, parallel workloads for supercomputing. It has significant advantages over Hadoop. It's used with high-performance links to share data between supercomputing centers.
http://sector.sourceforge.net/index.html
http://sector.sourceforge.net/pub/Sector%20vs%20Hadoop%20-%2...
That said, IPoIB should work just fine, and the main bottleneck currently is (Ethernet) latency. I'm running a couple of 1,6PB clusters (432 * 4TB) and can only get 20-60MBps on a single client with a 4kB block size, but got bored of benchmarking after saturating 5 concurrent 10Gb clients with a 4MB block size.
I do expect the RDMA situation to improve substantially over the next year or so, even if authentication will still be unsupported. The latter generally isn't a problem in HPC where stuff like GPFS lives (where you also have to trust every client). And they clearly want that market now that CephFS is finally deemed production ready.
It works with RDMA, has a POSIX layer, and is roughly equivalent to Lustre in performance in my tests, but 1° is very easy to setup (compared to Lustre) 2° has NFS actually working.