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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.
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