Moab has a very flexible and generalized definition of a node. This flexible definition, together with the fact that Moab must inter-operate with many resource managers of varying capacities, requires that Moab must possess a complete set of mechanisms for managing nodes that in some cases may be redundant with resource manager facilities. To accommodate all systems, Moab determines a node's configuration through the following approaches:
Resource Manager Direct Specification
Some node attributes may be directly specified through the resource manager. For example, Loadleveler allows a site to assign a MachineSpeed value to each node. If the site chooses to specify this value within the Loadleveler configuration, Moab obtains this information via the Loadleveler scheduling API and uses it in scheduling decisions. The list of node attributes supported in this manner varies from resource manager to resource manager and should be determined by consulting resource manager documentation.
Resource Manager Specified 'Opaque' Attributes
Many resource managers support the concept of opaque node attributes, allowing a site to assign arbitrary strings to a node. These strings are opaque in the sense that the resource manager passes them along to the scheduler without assigning any meaning to them. Nodes possessing these opaque attributes can then be requested by various jobs. Using certain Moab parameters, sites can assign a meaning within Moab to these opaque node attributes and extract specific node information. For example, setting the parameter FEATUREPROCSPEEDHEADER xps causes a node with the opaque string xps950 to be assigned a processor speed of 950 MHz within Moab.
Scheduler Specified Default Node Attributes
Some default node attributes can be assigned on a rack or partition basis. In addition, many node attributes can be specified globally by configuring the DEFAULT node template using the NODECFG parameter (i.e., NODECFG[DEFAULT] PROCSPEED=3200). Unless explicitly specified otherwise, nodes inherit node attributes from the associated rack or partition or from the default node template. See the Partition Overview for more information. Scheduler Specified Node Attributes
The NODECFG parameter also allows direct per-node specification of virtually all node attributes supported via other mechanisms and also provides a number of additional attributes not found elsewhere. For example, a site administrator may want to specify something like the following:
NODECFG[node031] MAXJOB=2 PROCSPEED=600 PARTITION=small
|These approaches may be mixed and matched according to the site's local needs. Precedence for the approaches generally follows the order listed earlier in cases where conflicting node configuration information is specified through one or more mechanisms.|