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## Overview

The Simple Linux Utility for Resource Management (SLURM) is an open source, fault-tolerant, and highly scalable cluster management and job scheduling system for large and small Linux clusters. SLURM requires no kernel modifications for its operation and is relatively self-contained. As a cluster resource manager, SLURM has three key functions. First, it allocates exclusive and/or non-exclusive access to resources (compute nodes) to users for some duration of time so they can perform work. Second, it provides a framework for starting, executing, and monitoring work (normally a parallel job) on the set of allocated nodes. Finally, it arbitrates conflicting requests for resources by managing a queue of pending work.

SLURM has been developed through the collaborative efforts of Lawrence Livermore National Laboratory (LLNL), HP, Linux NetworX, and PathScale. Linux NetworX distributes SLURM as a component in their ClusterWorX software. HP distributes and supports SLURM as a component in their XC System Software.

### Architecture

SLURM has a centralized manager, slurmctld, to monitor resources and work. There may also be a backup manager to assume those responsibilities in the event of failure. Each compute server (node) has a slurmd daemon, which can be compared to a remote shell: it waits for work, executes that work, returns status, and waits for more work. User tools include srun to initiate jobs, scancel to terminate queued or running jobs, sinfo to report system status, and squeue to report the status of jobs. There is also an administrative tool scontrol available to monitor and/or modify configuration and state information. APIs are available for all functions.

SLURM has a general-purpose plugin mechanism available to easily support various infrastructure. These plugins presently include:

- Authentication of communications: authd, munge, or none (default).
- Checkpoint: AIX (under development) or none.
- Job logging: text file, arbitrary script, or none (default).
- Node selection: Blue Gene (a 3-D torus interconnect) or linear.
- Scheduler: The Maui Scheduler, backfill, or FIFO (default).
- Switch or interconnect: Quadrics (Elan3 or Elan4), Federation ( IBM High Performance Switch), or none (actually means nothing requiring special handling, such as Ethernet or Myrinet, default).

### Configurability

Node state monitored include: count of processors, size of real memory, size of temporary disk space, and state (UP, DOWN, etc.). Additional node information includes weight (preference in being allocated work) and features (arbitrary information such as processor speed or type). Nodes are grouped into disjoint partitions. Partition information includes: name, list of associated nodes, state (UP or DOWN), maximum job time limit, maximum node count per job, group access list, and shared node access (YES, NO or FORCE). Bit maps are used to represent nodes and scheduling decisions can be made by performing a small number of comparisons and a series of fast bit map manipulations. A sample (partial) SLURM configuration file follows.

    #
    # Sample /etc/slurm.conf
    #
    ControlMachine=linux0001
    BackupController=linux0002
    #
    AuthType=auth/munge
    Epilog=/usr/local/slurm/sbin/epilog
    HeartbeatInterval=60
    PluginDir=/usr/local/slurm/lib
    Prolog=/usr/local/slurm/sbin/prolog
    SlurmctldPort=7002
    SlurmctldTimeout=120
    SlurmdPort=7003
    SlurmdSpoolDir=/var/tmp/slurmd.spool
    SlurmdTimeout=120
    StateSaveLocation=/usr/local/slurm/slurm.state
    SwitchType=switch/elan
    TmpFS=/tmp
    #
    # Node Configurations
    #
    NodeName=DEFAULT TmpDisk=16384 State=IDLE
    NodeName=lx[0001-0002] State=DRAINED
    NodeName=lx[0003-8000] Procs=16 RealMemory=2048 Weight=16
    NodeName=lx[8001-9999] Procs=32 RealMemory=4096 Weight=40 Feature=1200MHz
    #
    # Partition Configurations
    #
    PartitionName=DEFAULT MaxTime=30 MaxNodes=2
    PartitionName=login Nodes=lx[0001-0002] State=DOWN
    PartitionName=debug Nodes=lx[0003-0030] State=UP    Default=YES
    PartitionName=class Nodes=lx[0031-0040] AllowGroups=students
    PartitionName=batch Nodes=lx[0041-9999] MaxTime=UNLIMITED MaxNodes=4096

### Status

SLURM has been deployed on all LLNL Linux clusters having Quadrics Elan switches since the summer of 2003. This includes IA32 and IA64 clusters having over 1000 nodes. Fault-tolerance has been excellent. Parallel job performance has also been excellent. The throughput rate of simple 2000 task jobs across 1000 nodes is over 12 per minute or under 5 seconds per job.

For information about this page, contact slurm-dev@lists.llnl.gov.