Universal Rule

Book Reviews

Wednesday, November 5, 2003

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Dnevin asked: "If you scaled the number of G5 processors to equal that of earth simulator would the bigger G5 cluster approach or surpass the current number 1? Or would bandwidth, overhead issues kill cpu / linear peformance?" Here is my reply:

I believe the current Infiniband hardware is optimized for the 2200 cpus in the system. To increase the number of processors, you would have to improve the communication hardware significantly.
Communication is the real bottleneck, as seen in the efficiency of 80% with 256 processors and the efficiency of 60% with 2200 processors.
The price of the system might scale almost linearly, though, if you could just plug in additional switches. But the cost of the communications hardware could as well increase much faster than linearly when adding new processors.

So, you could build a G5 system surpasing Earth simulator, but the price could exceed $20 million. (But the price would be extremely cheap in comparison.)

Over 2000 readers in a day... -- Comment()
This is a new record (I believe) for this weblog. My story about Apple G5 dual supercluster has generated a lot of traffic, apparently. I slightly updated the text today. I also noticed some benchmark results of MVAPICH.

Rob Barris commented on the huge power consumption estimate: "I would not be surprised if a large fraction of the difference is accounted for by the external cooling machinery - compressors to make cold water for distribution are likely power hogs (as most refrigerators are)." Thanks for this insight. However, isn't this a case of moving heat from one place to another, and thus not too expensive? Of course, this depends on the actual mechanism which is used, and the system at Virginia Tech may well be rather inefficient.

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Radiofrequency Weapons: "Global security is running a fairly detailed and interesting story on E-bombs (not email bombs, rather electronic microwave weapons) taken from the IEEE Spectrum Online. We have long known (since the 1940's) about the effects that high energy weapons can have on electronic components from nuclear blasts, but this class of weapons is designed to exclusively attack electronic infrastructure."

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PC Magazine: Five Stars For Panther: "PC Mag gave the big black cat a five out of five star rating. I really like Panther, but I never would have imagined that this would happen. Pretty cool. PC users take note!"

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IPv4 - How long have we got? "The basic question is "how long can the IPv4 address pool last in the face of a continually growing network?" We've seen in the industry press at regular intervals dire reports that the IPv4 sky is falling and somewhere on the globe they've "'run out" of addresses. Once again it's probably time to take a more considered look at the problem and see what numbers come out from this exercise using data collected up to 2003."

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I noticed that Mellanox made in September a press release titled Virginia Tech Selects Mellanox Technology to Create the World[base ']s Largest InfiniBand Cluster: "The Virginia Tech cluster will feature 24 Mellanox 96-Port switches. Each switch has 1.92 Terabits of bandwidth that enable this cluster with over 44 Terabits of total bandwidth."