Configuring Scrub Tasks

How to configure automated scrubs of storage pools.

  2 minute read

A scrub is the process of ZFS scanning through the data on a pool. Scrubs help to identify data integrity problems, detect silent data corruptions caused by transient hardware issues, and provide early alerts of impending disk failures.

By default, TrueNAS creates a scrub task when new pool is created. The default schedule for a scrub is to run every Sunday at 12:00 AM. To edit the default scrub, go to Tasks > Scrub Tasks and click .

To create additional scrub tasks, you must first create a pool.

Create Scrub Task

To create a scrub task for a pool, go to Tasks > Scrub Tasks and click ADD. First, select a pool for the scrub task. Enter a number for the Threshhold days. The Threshhold days are the number of days before a completed scrub is allowed to run again. This controls the task schedule. For example, scheduling a scrub to run daily and setting Threshold days to 7 means the scrub attempts to run daily. When the scrub is successful, it continues to check daily but does not run again until seven days have elapsed. Using a multiple of seven ensures the scrub always occurs on the same weekday.

Select a schedule for the scrub task. If a custom schedule is desired, select Custom and fill out the custom scheduler to meet your needs. The custom scheduler can accept standard cron input strings for the Minutes, Hours, and Days. Unsetting Enabled only disables the schedule. You can still save the scrub task and enable it later.


Last modified August 31, 2020: Update scrub.md (bec27a54)