Everybody is looking to shake up the server business this days, it seems. But everyone had better get in line behind 3Leaf Systems, which is launching its much awaited "Aqua" system pooling and virtualization chipset and an intriguing x64 system to match. A little more than two years ago, 3Leaf Systems came out of stealth mode …
I'm generally a big fan of shared memory systems. However, there are a couple of issues. First is performance (of course) - off-board memory access and cache coherence overheads can be a big problem, although the appropriate workload and clever system software can help a lot (same with NUMA).
However, there is a bigger potential problem with availability. In general, any failure across the physical memory space of a shared memory machine can bring everything down. Basically if you double the number of components you double the number of hardware failures in a given period. Big iron hardware has lots of very expensive features to minimise this through error correction, redundancy and so on. A large shared memory machine made out of commodity stwo-socket servers isn't going to have such features. With non-shared memory models, and an appropriate application design (such as Oracle RAC or horizontal load balancers), then the failure of a single node won't bring the service down. With shared memory models (unless they've been able to do something very clever), the loss of a single node is likely to bring the whole thing down.
What apps will be able to take advantage of it? Very few can scale properly beyond say 8 or 16 CPUs. Of those that can, how many of them would be supported on 3leaf?
I recently got web pricing from HP for a c Class blade enclosure, redundant 10GbE/4Gb FC virtualconnect, 16 blades(192 cores), and 1TB of memory, with the fancy management software(excluding VMware) was about $150k, Add list pricing for a basic vmware install at another $75k(advanced version, not enterprise plus), seems like a better deal. Myself I like the HP blades since they have so many memory slots on them and the built in virtualconnect, and the price is good(because they can use smaller memory chips).
But I suppose there are some niche apps out there that can benefit from this 3leaf stuff I just don't know what they are myself.
So we're going to end up with monster servers virtualised to run single dinky VM's, and dinky servers 3Leaf'd to run single monster servers..
Supercomputer on the cheap?
So once the software would be able to cope with a very large number of servers and shared memory, would you be able, at least in theory, to build a relatively inexpensive supercomputer?
Virtual Iron all over again?