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OceanStor 9000 V300R006C00 Object Storage Service (Compatible with OpenStack Swift APIs) Administrator Guide 07

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Introducing Background Tasks

Introducing Background Tasks

By background task management, you can set priority, impact, and time policy for different types of background tasks and start, cancel, suspend, or recover the background tasks.

Schedule Management

The OceanStor 9000 supports schedule management of background tasks. By schedule management, you can set priority, impact, and time policy for some background tasks. Background tasks for which schedule management can be performed are classified into one-off tasks or periodic tasks based on different time policies, as shown in Table 17-1.

Table 17-1  Background tasks for which schedule management can be performed

Operation Period

Task Type


One-off task

One-off Data Migration

Do not modify the time policy of a one-off task.

Periodic task

  • Data Migration
  • Data Consistency Scan


The priority level ranges from 1 to 100. 1 indicates the highest priority and 100 indicates the lowest priority.

  • 1 to 20: high priority
  • 21 to 50: medium priority
  • 51 to 100: low priority

The task scheduling priority is as follows: the system schedules tasks with high priority. If tasks have the same priority, the system schedules one-off tasks. If tasks have the same priority and are all one-off or periodic tasks, the system schedules the suspended tasks. If all the conditions are the same, the system schedules tasks in the sequence of task creation time.


Impact of a task is the occupation upper limit of system resources for task scheduling.

Impact includes two properties:

  • Period: Defines the start and end time of a day in a week. The unit is week.
  • Resource occupation upper limit: subject to the CPU occupancy rate. The CPU occupancy rates of high, middle, and low impact are 80%, 50%, and 30% respectively. The policy of the default impact cannot be changed. Users can create other types of impact.

    If a background task exceeds the CPU occupancy rate within the impact period, the system suspends the task and checks the CPU occupancy after a period of time. If the background task does not exceed the CPU occupancy rate any more, continue the task. If the background task still exceeds the CPU occupancy rate, the task remains suspended.

Time Policy

Task scheduling period. One-off tasks are event-triggered. Periodic tasks are automatically schedules based on the time policy.

Periodic tasks support two types of scheduling periods:

  • By Fixed Frequency
  • By Fixed Time

Scan Ratio

Ratio of the data consistency scanning speed to the data consistency scanning depth. The values of the speed and depth range from 0 to 5 and cannot be both 0.

Background Task Status Conversion

Table 17-2 describes all background task states.

Table 17-2  Running Status




Tasks wait to be scheduled.


Tasks are running.


Tasks are being scheduled.


Tasks are being paused.


Tasks are paused and can be manually recovered to run.


Tasks are being suspended.


Due to unreasonable scheduling time or priority preemption, tasks may be suspended and then are automatically recovered to run. Tasks are suspended and can be automatically recovered to run.


Tasks are being canceled.


Tasks are canceled manually. After a one-off task is canceled, the task becomes invalid. After a task that is periodically performed is canceled, the task can be recovered in the next period.


Only a one-off task can be in the completed state. After a periodic task is completed, it will queue for being scheduled again.

Figure 17-1 describes the conversion process of system status.

Figure 17-1  Background task status conversion

Updated: 2019-04-28

Document ID: EDOC1000122524

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