Core reservation in PBS
Researchers who bother to read the Acceptable Usage Policy may have noticed there is a clause which states: Users must abide by the ratio of 2GB of RAM (memory) per allocated core. Usage of the pmem directive should also be…
10 million CPU hours
This weekend we passed the 10,000,000 CPU hours mark. This is the sum total of CPU hours of all clusters our users have run jobs on since 2010: Roughly the equivalent of running a single core computer for 416,000 days…
High Memory Nodes
We have installed two high memory DELL R820 servers into the 800 series. Each server has four sockets with six cores of 2.4GHz each. There are also thirty two 32GB DIMMS making up 1TB of RAM, although these memory chips …
Say hello to HAL
Over the past few months we’ve been referring to a new type of scheduler that we’ve been testing. We decided to move away from PBS as MAUI is no longer being maintained. The scheduler we have selected, SLURM, is …
Berkeley Lab Checkpoint/Restart
Berkeley Lab Checkpoint/Restart has been installed on the SLURM cluster. This allows users to checkpoint a job, cancel it and then resume the job at a later date. The executable is started with the cr_run wrapper: cr_run /home/andy/ram.pl >> /home/andy/ramtest.out…
SLURM and memory management
SLURM allows a DefMemPerCPU and a MaxMemPerCPU to be set. If a user does not set a memory limit the default will be used. This is normally set to MaxMem/NumCores. As memory is a consumable resource (SelectTypeParameters=CR_Core_Memory) MaxMemPerCPU serves not
…SLURM job preemption
SLURM provides a preemption mechanism to deal with situations where cluster become overloaded. This can be configured in several ways:
FIFO:
This is the most simplistic method of queueing in which there is no preemption, jobs come in, queue and …
Where are all the HPC servers disappearing to?
Those users still making use of hpc.uct.ac.za will have noticed that a few worker nodes have vanished. As mentioned previously we’re investigating a new scheduler, SLURM, Simple Linux Utility for Resource Management. SLURM is a very different animal to
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