BEOWULF cluster hangs

Jeff Nguyen jeff at
Thu Sep 26 09:39:48 PDT 2002

2.4.7 kernel performs horribly on the dual Xeon platforms because it does not 
support IRQ balancing and DMA transfer on the IDE bus. If you are using an
IDE disk on the nodes, disk performance is very slow which might affect your

  ----- Original Message ----- 
  To: beowulf at 
  Sent: Thursday, September 26, 2002 7:16 AM
  Subject: BEOWULF cluster hangs

  Since a month we have a LINUX BEOWULF cluster, the clusters contains 7 P4 dual processor 2GHz computers, with 8Gb of RAM per machine. For our network we have used Gigabit ethernet. 

  The problem we have with our cluster is as follows. 
  When running large computational fluid simulations the simulation starts to slow down. At some point the response of the computer is so poor that we have to kill the simulation. In a worst case when the simulation was running overnight the computer hangs and a reset of the computer is necessary. 
  Nevertheless, even when we manage to kill the simulation in time the computer remains very slow and a reboot is necessary to regain full computer power. 

  My first suspicion was that the computer simply started swapping, but there is no swap space being used, instead free RAM memory is still apparent 
  (between 5-10%) and only 90% of the RAM is in use whereby 50% is cached and another 50% is in usage. In addition the cpu usage is very low as well. 

  May be it is of use to mention that this problem occurs with both sequential and parallel simulations. 

  On our cluster we are running RH7.2 with the LINUX kernel version 2.4.7-10. We have set-up our cluster using oscar-1.2.1rh72. The /home partition on the world client is a shared via the network using NFS. 

  /etcfstab /home nfs rw 0 2 

  1) In case anyone could do me some suggestions why our computers are slowing down/hanging or if some one has got a similar experience please let me know. 
  2) To my understanding the most important indicators to indicate the computer usage are: 
  - memory usage 
  - cpu usage 
  Are there other key components/indicators which could lead to a reduction in computer performance, and if so how can I see the status of them. 


| Dr. Govert de With     Research Fellow                     |
| Fluid Mechanics Research Group                             |
| University of Hertfordshire                                |
| Tel: 01707 284124 Fax: 01707 285086                        |
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