About the Special User default

You can use the special user default to reduce the amount of share-tree maintenance for sites with many users. Under the share-tree policy, a job's priority is determined based on the node the job maps to in the share tree. Users who are not explicitly named in the share tree are mapped to the default node, if it exists.

The specification of a single default node allows for a simple share tree to be created. Such a share tree makes user-based fair sharing possible.

You can use the default user also in cases where the same share entitlement is assigned to most users. Same share entitlement is also known as equal share scheduling.

The default user configures all user entries under the default node, giving the same share amount to each user. Each user who submits jobs receives the same share entitlement as that configured for the default user. To activate the facility for a particular user, you must add this user to the list of grid engine users.

The share tree displays “virtual” nodes for all users who are mapped to the default node. The display of virtual nodes enables you to examine the usage and the fair-share scheduling parameters for users who are mapped to the default node.

You can also use the default user for “hybrid” share trees, where users are subordinated under projects in the share tree. The default user can be a leaf node under a project node.

The short-term entitlements of users vary according to differences in the amount of resources that the users consume. However, long-term entitlements of users remain the same.

You might want to assign lower or higher entitlements to some users while maintaining the same long-term entitlement for all other users. To do so, configure a share tree with individual user entries next to the default user for those users with special entitlements.

In Example A, all users submitting to Project A get equal long-term entitlements. The users submitting to Project B only contribute to the accumulated resource consumption of Project B. Entitlements of Project B users are not managed.

Example 5–2 Example A

Compare Example A with Example B:

Example 5–3 Example B

In Example B, treatment for Project A is the same as for Example A. But all default users who submit jobs to Project B, except users A and B, receive equal long-term resource entitlements. Default users have 20 shares. User A, with 10 shares, receives half the entitlement of the default users. User B, with 40 shares, receives twice the entitlement as the default users.