KEPLER, a selfmade Cluster in TuebingenHeidelberg 23 July 2001 Harry Yserentant, University Tuebingen, presented some numerical applications that run on the Pentium Cluster KEPLER as well as its architecture. The users and the University has beneath PCs small compute servers, 4 processors and 8 GB memory, and can access the supercomputers in Stuttgart and Karlsruhe. Thus there is a gap which now is filled by a big PC cluster. It is equipped with dual Pentium III, 650 MHz, and 1 GB memory per node. They use BX motherboards and have 32 bit/33 MHz PCI bus. The nodes are connected with two networks. Ethernet, 100 Mbit, is used to start nodes and processors, while Myrinet is for the direct exchange of messages of the nodes.
The measured transfer rate of 115 MB/s comes very close to the maximal possible transfer rate of 133 MB/s of the PCI bus. Thus Myrinet allows an access/transfer speed that is similar to the local memory access. All the nodes are diskless except five, which are equipped with four 40 GB IDE hard-disk. These nodes serve as MPI I/O nodes when several independent jobs run on part of the cluster. The user has GNU compilers gcc and g++ and a Fortran-compiler. Totalview is the debugger and Vampit/Vampirtrace from Pallas are the profilers. Libraries as BLAS and Lapack support the numerical computing. The cluster management software is SCore. It achieves high transfer rates as SCore is a special user space communication system. It gives the applications direct access to the network interface and avoids copy and buffer operations. The Linpack benchmark scales very well, on one processor .517 GFlop/s is achieved, on 196 the Rmax is 96.25 GFlop/s, an improvement factor of 186. Compared to the peak performance of 128 GFlop/s it get 75.4% of it in the Linpack. The university plans to extend this cluster by another 32 nodes, which they hope to install perhaps this year. It consists of 32 nodes, serverset chipset, PCI 64/66 MHz, two way interleaved memory access, dual PIII 1 GHz and 1 GB memory as well as a harddisk with more than 40 GB per node and graphics. The harddisk is used as the University participates in the ASPIC project, Application Service Provider for integrated technical-scientific simulation on high-performance PC clusters. It is funded by Baden-Wuerttemberg, partners are the University and science + computing from Tuebingen.
Uwe Harms |
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