2/3 of the speed of light (in vacuum) is actually about 200000 km/sec. Otherwise the parent poster is correct, though. There is no big difference between the speed of signal propagation in fiber vs copper.

One major advantage of IB here is that it natively supports multipathing; there's no need to avoid loops in the graph either by topology or by using spanning trees. This allows one to build networks with decent bisection BW without needing big and expensive über-switches.

There are a few efforts to bring similar capability to ethernet as well, TRILL and 802.1aq, AFAIK neither of which is ratified at the time of writing this.

I'll assume you know more about this than me, but he did say that the nodes are going to be wired with 4x GigE. Might there be a penalty bridging from that to IB rather than 10GigE?

The way I read it, it means that the nodes have 4 1 GbE ports builtin on the MB. If you're going to use IB, you'll by separate PCIe IB cards for each node. The 1GbE ports can then be used to run management traffic etc. Or left unused, there's no law saying you have to use them all, and since 1GbE ports are practically free it's not like you're leaving any money on the table either.

Wrt RDMA over ethernet, iWARP this and that, yes I know it exists. My point was that RDMA has been supported on IB since day 1, the software stack is mature and widely used, which can't be said for ethernet RDMA. Since IB infrastructure so far is cheaper there's really no reason to go with 10GbE.

That's not to say that 10GbE is useless. Of course it's useful, e.g. if you run high-bandwidth services over TCP/IP accessible from outside the cluster. But that's not what you're doing on a cluster. A cluster interconnect is typically used for MPI and storage, both of which can run over RDMA, avoiding the by comparison heavy-weight TCP/IP protocol. And of course, at some point 10GbE will replace 1GbE as the cheap builtin stuff on MB's.

Shouldn't you have figured out answers too all these (simple) questions before ordering several million $$$worth of hardware? Sheesh.. As for you specific questions: - IB vs. 10GbE: IB hands down. Much better latency and more mature RDMA software stacks (e.g. for MPI and Lustre). Cheaper and higher BW as well. - GPU: NVidia Fermi 2090 cards. CUDA is far ahead of everything else at the moment.

Most codes can't deal with node failure. So far it seems the solution is to checkpoint frequently (say, once per hour). There's not much else that is sensible. E.g. running pairs of nodes in lockstep is more expensive than an IO subsystem capable of the checkpointing.

This one uses SPARC chips designed and fabbed (IIRC?) by Fujitsu. Sun/Oracle has nothing to do with it. AFAICT the politics behind this machine is that a few years ago NEC pulled out from the project to design a next generation vector chip for use in a Japanese Earth Simulator follow-up. Hence the project resorted to the Fujitsu SPARC chips, which are not really designed for HPC but are still a domestic design. I wouldn't expect this machine design to become popular outside Japan.

Ah, but even Conservapedia isn't safe, as trolling it is a popular (?) pastime: The Conservapedia trolling game.

So the FSF should not put up a web page explaining which licenses they recommend and why, because someone on the Internet might disagree? Seriously?

Persistency: once eth0, always eth0 - this is what most commentators here seem to think this is all about, but it's already taken care of by udev with most modern distributions.

To some extent. The persistency is taken care of by adding state to the system, that is, by storing the MAC's somewhere. That fails e.g. if you switch out a broken NIC, or if due to some hw failure you move the HD to another identical server.

Naming: The article says they're changing the naming. This is what makes no sense. It's not "required." ethx is just fine, as long as the names are enumerated consistently (meaning that on two "identical" boxes, the order is identical based on physical port).

IIRC the justification for this is that using ethX would race with the original kernel names. This thingy is based on udev, when the kernel boots devices are given ethX names and then udev rules rename them according to bios names, or PCI bus order etc.

Seems nowadays quite many of the pro(sumer) sound cards are external ones connected via USB.

Presumably the idea being to isolate the DAC from all the electrical noise inside the case?

What about latency on these things? One would imagine that one extra protocol hop would add latency, and then traffic would have to be shared with other traffic on the same bus? I mean, people doing audio production seem to be sensitive to latency, to the point that Linux users use the RT kernel. Is USB really up to it?

Replying to myself, TFA contains some info about this. Hey, this is slashdot, who has time to read TFA?

So you're claiming ACID; IOW you are saying your system provides consistency as per the definition used in CAP?

How do you deal with network partitions? That is, per the CAP theorem, if you have C, is your system CA or CP?

Thanks,

NIH?

As others have mentioned, this is nothing but the latest attempt to kill off the used books market. The textbook industry is just a big racket.

Curiously, the obvious solution of using widely available free online textbooks is ignored (see e.g. http://theassayer.org/ for a directory). Oh yeah, can't do that because we "need to save the textbook industry".

Of course, free online textbooks aren't the answer to everything, say for some grad-level specialized course the selection of appropriate textbooks might be quite limited, if available at all. But for all those massive "XXX 101" courses, surely the free online resources are plentiful, and some even very good quality. Or maybe even better, as a free online textbook writer has no incentive to bulk up the book with useless fluff, which just wastes student time when reading.

What is usually done over here, at least in the math and physics departments, is that homework problems are separate handouts. That way it doesn't really matter that much which edition of a textbook the students use.