User's Manual

142 Migration, release, recall, and deletion
Note that resource allocation requests from different partitions can have different drive and priority
policies, and that the same media pool cannot be assigned to several partitions. For more information on
parameters for resource allocation, see ”System allocation and job priority policy” on page 142 and
”Partition allocation and job priority policy” on page 144.
Job priorities
When a new job is created, if all of the requested resources are available in the FSE implementation,
Resource Manager allocates them and the job starts performing its task immediately. If some resources are
not available, a resource request of the job is put into the resource allocation queue of the Resource
Manager, and the job waits for availability of the resources.
In case there are too many jobs already running for the corresponding FSE partition, the newly created job
is not allowed to request resources yet, but is put into the state ”pending” instead. Such pending job waits
until the current job count for the FSE partition decreases below a threshold value, and can only request the
resources from the Resource Manager afterwards. Pending jobs are processed in the “first come first
served” order. The threshold job count is defined by the MaxNumDrives variable (specified in the FSE
partition configuration file) as follows:
IMPORTANT: The status pending is applicable only for jobs that can be run on a particular FSE
partition: migration, recall, reorganization, and maintenance jobs. Administrative and backup jobs are FSE
implementation-wide jobs. They are immediately started or queued in the resource allocation queue, no
matter how many jobs are already running in the FSE implementation.
When the resource request of a job is put into the resource allocation queue, the job is assigned an initial
priority. When a new job is put into the queue, the priorities of all existing resource requests are
recalculated; the priority of each job is then modified according to the elapsed time and the phase of the
job. The resource request is then processed according to its job priority. Each time a resource is freed, the
queue is checked again to allocate the free resource.
IMPORTANT: Only jobs with the status waiting for resources have priorities assigned.
For details on priority calculation, see ”Priority calculation” on page 146.
System allocation and job priority policy
The system allocation and job priority parameters are read by the Resource Manager upon its startup.
System allocation and job priority policy parameters
The configuration parameters for the system along with their definition and impact are listed below.
Maximum number of drives for migration (SystemMaxNumDrivesMigration)
ThresholdJobCount = 3/2 * MaxNumDrives
Definition Maximum number of drives that can be used for migration by all FSE partitions.
Impact The purpose of this parameter is to prevent migration jobs from using all the drives in the
FSE implementation. By limiting drives for migration, you ensure that drives remain
available for other jobs (recall, administrative, recovery…). You should carefully balance
resources according to your environment.