Issues, but no real answers

The Beowulf mailing list provides detailed discussions about issues concerning Linux HPC clusters. In this article I review some postings to the Beowulf list on performance measurements and Microsoft's foray into the HPC market (nice historical perspective here) which resulted in a good and timely discussion about Linux distributions for the HPC world. While these discussions were from 2004 and a bit on the older side (aren't we all?), they do provide some good insights into the these continuing discussions

G5 Performance and Benchmarks

This Beowulf list thread started when the Eugen Leitel posted a forward from another mailing list asking about Apple G5 performance, particularly on the computational chemistry QM and MD codes (the original poster was Joe Leonard). Eugen also forwarded a response to Joe's initial posting from the other list. Mike McCallum had tested dual G5's and found them to be near the top in price/performance, especially using the IBM compilers. He also found the built-in GigE to be quite good for scaling on NAMD and CHARMM which according to Mike scale well with GigE (these were based on some benchmark numbers that Mike posted).

Bill Broadley was the first to reply with a request for some clarification of some of the test results that Mike had posted. He also took issue with some of the conclusions that Mike made regarding the scalability of NAMD and CHARMM on GigE vs. Myrinet. Michael Huntingdon then posted that he thought that the Itanium 2 was a good solution based on the performance numbers.

Joe Landman took issue with the idea of using SPEC numbers as a "good" predictive indication of performance. Joe also points out the benchmarks posted by Mike McCallum may have some flaws because of compilers and compile options. Joe also had problems with recommending Itanium 2 processors for all HPC applications. Joe pointed out that for Bioinformatics applications, Itanium 2 processors don't compare well to other processors.

A frequent contributor, Mark Hahn, joined in to say that he had done a small analysis of the SpecFP benchmarks. His goal was to point out that the SpecFP scores of some machines are due to a small subset of the SpecFP scores. He sorted the scores for each machine and omitted the top scores and plotted the results. Based on his analysis he concluded that the PowerPC 970 was good for cache friendly codes and codes that could perform two vector mult-add operations per cycle; the Itanium 2 is great if your code is cache friendly, your code is amenable to the pipelining required by EPIC (the Itanium 2 architecture), and you can afford them; and Opterons are great if your working set makes caches less effective.

Greg Lindahl posted a response to Mark's analysis. He didn't think the analysis was valid because the scores were not normalized to make their absolute scores valid. Greg also took issue with the phrase, "...if you can afford them..." in regard to the Itanium 2. Greg's point is that you find the best price/performance and buy those systems or you buy the most performance for a given price. Both of those approaches don't care about the cost of a single system, just the performance and cost of the entire cluster.

Windows HPC Edition and Linux Clustering

As would be expected, this thread brought up a lot of opinions and insights from the list membership. On May 25, 2004 Eugen Leitel posted an article describing how Microsoft was creating an HPC version of Windows (Now available as Windows Compute Cluster Server 2003). Of course, there were the immediate comments about seeing hundreds of nodes all getting the "blue screen of death" at the same time. Of course there is always a chuckle about these comments, but there are some real issues behind Microsoft's entry into this space.

Robert Brown started off the discussion by writing a "few" comments about Microsoft's motives for entering the HPC market. Shortly there after Joe Landman jumped in to say that companies don't really have nefarious motives behind their efforts. In his opinion he thought that most of their efforts are clearly discernible from their basic goals (usually involving making lots of money). Douglas Eadline, editor of ClusterMonkey, posted that he thought there were two reasons that Microsoft is entering this market. The first reason, like any corporation, is profit. He noted that the article stated that Microsoft was focusing on the financial and cycle scavenging markets where the return on the investment is good. The second reason was for competitive reasons. He suggested that they are trying to limit "Linux creep" and that using Linux to build airplanes, find oil, and search the genome have added some legitimacy to Linux in the data center. His final comment, "I think we just got legit.", was of a positive nature because the entry of a big company often helps legitimize/solidifying markets.