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Apple Wins VT in Cost. vs. Performance
danigiri writes "Detailed notes about a presentation at Virginia Tech are posted by by an attending student. copied most of the slides of the facts presentation and wrote down their comments. He wrote some insightful notes and info snippets, like the fact that Apple gave the cheapest deal of machines with chassis, beating Dell, IBM, HP. They are definitely going to use some in-house fault-tolerance software to prevent the odd memory-bit error on such a bunch of non-error-tolerant RAM and any other hard or soft glitches. The G5 cluster will be accepting first apps around-November."
mfago adds, "Apple beat Dell, IBM and others based on Cost vs. Performance alone, and it will run Mac OS X because 'there is not enough support for Linux.'"
One of the primary concerns for a multi-node cluster is insured latency among all components within the cluster. It doesn't have to be the fastest, it just needs to insured exacting timing for latency across all nodes. IBM can do this with their "wormhole" switch routing on SP and has done this with Myranet on their Intel X-series clusters.
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From most of my reading with Infiniband, it was designed from the ground up as a NAS style solution, than for large multi-node cluster computing. I'm curious as to if they have any issues with cluster latency.
http://www.nwfusion.com/news/2002/1211sandia.ht
The primary timings and white papers I've seen published for Infiniband have been for small clustered filesystem access. Although it's burst rate is much higher than Myranet, it's hard to find any raw retails for their multiple node latency normalization.
I hope it scales, since Intel's solution appears to be less cost prohibitive than some of the other solutions offered on the market, and would really open up the market even for smaller clusters (16-36 node) for business use.
A Multiplayer Strategy Game for Mac OS X, Windows, and Linux
As an American company, Dell is a huge disgrace. Please read the "Environmental Report Card" produced by the Silicon Valley Toxics Coalition. Dell received a failing grade and is little better than Taiwanese companies, which are notorious for destroying the environment and the health of workers. Dell even resorted to prison labor to implement its pathetic recycling program.
2. Even if somehow a none-thermal bit error occurs, each node has 4GB RAM. The probability of it being in an OS or application critical (especially given the converging nature of many long running calculations) piece of RAM as opposed to an empty piece of RAM is small.
Think before you post. The failure rate is constant in each memory chip (actually it goes up a bit with higher capacity due to higher density). Unless you setup the memory to be redundant (which the G5 can't do either...) you will experience MORE errors since a good OS tries to use the empty memory for things like file buffers.
How many of you are reading this from a desktop without ECC RAM that has an obnoxiously huge uptime? ECC is a non-issue in a well-cooled cluster of desktop cased machines.
Sigh... this is a 2200-cpu *cluster*. Here's a primer on statistics. Assume the probabiliy of a memory error is 0.01% for some time interval (say a week or month). The likelyhood for a perfect run is then 99.99% on your single CPU, which is just fine. Running on 2200 CPUs, the probability of not having any errors is 0.9999^2200=0.8, or 20% probability of getting memory-related errors somewhere in the cluster.
The actual numbers aren't important - it might very well be 0.01% probablility for an error per year, but the point is that when you run things in parallel the chance of getting a memory error *somewhere* is suddenly far from negligible.
ECC is a cheap and effective solution that almost eliminates the problem. Incidentally, one of the challenges for IBM with "Blue Gene" is that with their super-high memory density even normal single-bit ECC might not be enough.
But, what do I know - I've only got a PhD from Stanford and not VT....