Stokes available following upgrade
This article is outdated - use this information at your own risk!
Posted on 24 August 2010
ICHEC is pleased to report that this afternoon access to Stokes was restored. The upgrade went as planned and the hardware is performing very well. The majority of packages have been rebuilt to exploit the new hardware. 3840 cores based on the Intel Westmere architecture are now available. The image below shows one of the 320 new compute blades.
While you will still need to provide your project code in job submission scripts, project accounts will not be charged for resources used until September first. This is an opportunity to tune and test codes on the new system without using project hours. However it is likely that during this initial period Stokes will need to be taken offline again periodically as fine tuning continues.
The new compute nodes have 12 rather than 8 cores per node. Therefore all Stokes PBS job submission scripts must now have the ppn value set to 12 rather than 8. You may also have to update package specific command line arguments or configuration files to accommodate this change.
If you compile your own software we strongly encourage you to rebuild your software and optimise it for the new architecture. ICHEC is happy to assist with this process. Along with all other Stokes infrastructure the login nodes have been retained. This means that the login and compute nodes have different processors which can have implications for those building their own software especially if configure scripts are used. If you think you are affected by this but are unsure of the implications contact ICHEC for assistance.
Please note that following the upgrade Stoke's SSH host ID has changed this means that you may see an authentication warning when you first try to connect. The solution to this is to remove the old ID from your known hosts file or equivalent depending on your SSH client.