Administrator's Guide

Linpack
Linpack is an industry standard cluster performance test used for submitting numbers to the Top
500 Supercomputers list. The test is implemented to run separately on each node using all CPU
cores and about 80% or less of memory. Two parameters need to be specified: Mem(GB) and
Mem(%). Mem(GB) is the total memory in gigabytes on each node, and Mem(%) is the percentage
of total memory used in the test. By default, this test will not give cluster-wide performance, but it
exercises CPU and memory at the same time, and it provides another set of numbers you can use
to compare the performance among the cluster nodes. The amount of memory required is set to
auto by default – this will run each node at the specified percentage of the memory available. For
example, using auto and 80%, a 2 GB node will use 80% of 2 GB, while a 16 GB node will use
80% of 16 GB. The amount of memory used on any head node is adjusted to allow for increased
memory consumption on head nodes. The default Linpack test run performs three iterations of the
test using the same input data for each run. To limit the number of iterations to one, select the Single
Pass option.
Netperf
Netperf is a benchmark used to measure network performance (for example, GigE and 10GigE).
It currently provides tests for unidirectional throughput. You must select TCP (TCP_STREAM) or UDP
(UDP_STREAM) protocol. The first half of the selected nodes receives messages from the second
half. For example, in a 10 node cluster, node 5 sends to node 0; node 6 sends to node 1; node
7 sends to node 2; and so on. An even number of nodes must be selected to run this test.
InfiniBand verbs tests
This is a collection of InfiniBand verbs bandwidth/latency performance tests provided with OFED.
Verbs-layer performance is usually higher than what is reported by the MPI-level tests, such as
Pallas. The InfiniBand verbs test (shown in the GUI as ib_send_bw) is selected by choosing the
test name from the first two spin boxes. These selections will update the test button used to run the
test. Test options can be specified in the Options box. Please refer to the documentation for each
individual InfiniBand verbs test for the available options. Some of the useful options include –a to
include all message sizes, and –b for bi-directional test. The node settings are identical to the
Netperf test above. These tests are only available with the InfiniBand interconnect on non-QLogic
IB hardware.
Deviation test
This test measures the consistency of bandwidth and latency between nodes using MPI over IB.
The node settings are identical to the Netperf test above. This test is only available with the InfiniBand
interconnect on QLogic IB hardware.
Monitoring tests and viewing results
The nodes monitoring window
The bottom left window on the Cluster Test interface is the nodes monitoring window. It can be
resized to give more space to the test output window.
This window indicates whether a node is active (online) or inactive (offline).
Monitoring tests and viewing results 15