Platform LSF Administration Guide Version 6.2

Understanding Advance Reservations
Administering Platform LSF
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Understanding Advance Reservations
Advance reservations ensure access to specific hosts during specified times. An advance
reservation is essentially a lock on a number of processors.
Each reservation consists of the number of processors to reserve, a list of hosts for the
reservation, a start time, an end time, and an owner. You can also specify a resource
requirement string instead of or in addition to a list of hosts.
During the time the reservation is active, only users or groups associated with the
reservation have access to start new jobs on the reserved hosts. The reservation is active
only within the time frame specified, and any given host may have several reservations
in place, some of which may be active at the same time.
When an advance reservation becomes active, LSF attempts to start all jobs that
reference the reservation. By default, jobs that are already running on the hosts may
continue, even though they do not reference the reservation. However, if a job that
references a reservation is pending because the host has reached its job slot limit, LSF
frees up a job slot on the host by suspending one of the jobs that does not reference the
reservation. This is the only case where advance reservation overrides another LSF job
scheduling policy.
Reservations can also be created for system maintenance. If a system reservation is
active, no other jobs can use the reserved hosts, and LSF does not dispatch jobs to the
specified hosts while the reservation is active.
Only LSF administrators or root can create or delete advance reservations. Any LSF user
can view existing advance reservations.
LSF treats advance reservation like other deadlines, such as dispatch windows or run
windows; LSF does not schedule jobs that are likely to be suspended when a reservation
becomes active. Jobs referencing the reservation are killed when the reservation expires.
LSF administrators can prevent running jobs from being killed when the reservation
expires by changing the termination time of the job using the reservation (
bmod -t)
before the reservation window closes.
Open advance reservations allow jobs to run even after the associated reservation
expires. A job with the open advance reservation will only be treated as an advance
reservation job during the reservation window, after which it becomes a normal job. This
prevents the job from being killed and ensures that LSF does not prevent any previously
suspended jobs from running or interfere with any existing scheduling policies.