The Half-Life Factor

Half-life is how fast the system “forgets” about a user's resource consumption. The administrator decides whether to penalize a user for high resource consumption, be it six months ago or six days ago. The administrator also decides how to apply the penalty. On each node of the share tree, grid engine software maintains a record of users' resource consumption.

With this record, the system administrator can decide how far to look back to determine a user's underusage or overusage when setting up a share-based policy. The resource usage in this context is the mathematical sum of all the computer resources that are consumed over a “sliding window of time.”

The length of this window is determined by a “half-life” factor, which in the grid engine system is an internal decay function. This decay function reduces the impact of accrued resource consumption over time. A short half-life quickly lessens the impact of resource overconsumption. A longer half-life gradually lessens the impact of resource overconsumption.

This half-life decay function is a specified unit of time. For example, consider a half-life of seven days that is applied to a resource consumption of 1,000 units. This half-life decay factor results in the following usage “penalty” adjustment over time.

• 500 after 7 days

• 250 after 14 days

• 125 after 21 days

• 62.5 after 28 days

The half-life-based decay diminishes the impact of a user's resource consumption over time, until the effect of the penalty is negligible.

Override tickets that a user receives are not subjected to a past usage penalty, because override tickets belong to a different policy system. The decay function is a characteristic of the share-tree policy only.