The computings racks are connected to five racks mounted on a Lustre shared filesystem with a total capacity of 5 PB useful.

Cooling is provided by a high efficiency warm water system directly in the nodes (mode DLC Direct Liquid Cooling).

The request for allocation of computing hours on this cluster is the subject of two campaigns per year(autumn and spring) through the DARI procedure.

Architecture of Occigen

Description

The machine is cut into a rack. A rack includes :

• A power supply unit for power supplies
• A block containing the redundant distribution services of the internal warm water circuit.
• 5 chassis. Each chassis is composed of 9 computing blades. These blades contain 2 nodes.
• The processors of the connection nodes are Intel 12-Cores E5-2690 V3.

In total, the Occigen cluster consists of 3367computenodes and therefore has 86048cores.

The network used to connect the nodes to each other is an Infiniband network (IB 4x FDR). The topology of the network is in the form of a Fat tree pruned. The network is non blocking within the chassis. Each group of 18 nodes that share the same switch in a chassis can be reached without restrictions. The “ascending” links from a switch chassis to the higher-order switches are divided by two. For 18 nodes, only 9 uplinks are used.

There are two types of filesystems :

• The /scratch (used to store the results of the calculations is of the Lustretype. It has more than 5 PB of usable space and a maximum bandwidth that exceeds 105 GB/s.
• The /home is a Panasas type, it is used to store the codes to be executed, it has a surface area of 260 TB and a bandwidth of 10 GB/s.

To store the results more securely, each node of the machine accesses the /store file system. This is also a Lustre filesystem, but with advanced security mechanisms (duplicate storage and tape storage).It must be used to ensure that the results are properly stored.