Computational Facilities

A wide area of LTT activities comprise the development and use of CFD-based analysis and optimization methods in a variety of application domains. The majority of the routinely performed computations are large scale ones and, thus, computationally demanding. These are all performed on the high-performance platform “VELOS” with 3 clusters. Each cluster consists of a number of interconnected CPUs (nodes) employing the TCP/IP protocol. In particular:

  1. The first cluster consists of 22 nodes (32bit, 35 cores in total). Its total RAM is 20GB, varying from 512MB to 2GB on each node. The operating system is Linux (Fedora).
  2. The second cluster consists of 30 nodes (64bit, 80 cores in total). Its total RAM is 100GB, varying from 1 to 4GB on each node. The operating system is Linux (Fedora and CentOS).
  3. The third cluster comprises 38 blade nodes (64bit) with 2 Quad core Xeon CPUs each, summing up to 304 cores. The nodes have 8GB or 16 GB RAM, with a total of 480 GB for this cluster. The operating system is Linux (CentOS).

The necessary services required for communication and data storage are handled by three dedicated servers, with the Network Information Service (NIS, holding the necessary user information) and Network File System Service (NFS, for file sharing).

Time consuming numerical simulations employ the MPI and PVM protocols, according to the MIMD (Multiple Instruction Multiple Data) model. Parallel processing with the SIMT (Single Instruction Multiple Thread) model is also performed using Graphics Processing Units (GPUs, NVIDIA's Ge-Force GTX 280 and GTX 285) installed on some nodes.

The 3 clusters of “VELOS” have also been used to run Grid-enabled CFD and optimization software. Regarding Grid Computing, the Grid interconnection is based on 3 layers of middleware, namely GridWay, Globus Toolkit and Condor. GridWay is used as the resource management software on the Grid. It unifies all Grid resources under a common queue and performs matchmaking according to requirements and rank attributes for each job. Once the Grid resource is selected, GridWay posts the job to the Globus Toolkit. This is installed on the front-end of each cluster and provides the framework for the interconnection of remote resources, user authentication, information services and gateways to which jobs are submitted. Globus posts the job to Condor, the local resource managment software of each cluster, which performs matchmaking and job monitoring on this cluster.