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Run a pool scrub

A scrub reads every block on the ZFS pool and verifies checksums. It catches silent bit rot before it spreads. The pool stays online during a scrub; performance may dip.

Reference: Backups and pool health.

When to run one

Situation Guidance
Routine Monthly — TrueNAS can schedule this automatically
After replacing a drive Run a manual scrub once resilver completes
After checksum errors Run scrub, then check SMART on suspect disks
Never needed for "speed" Scrubs are for integrity, not performance tuning

A full scrub on ~100 TB usable space can take many hours. Start off-peak if the family is streaming or copying large files.

Check if a scrub is already scheduled

  1. Open dsm.saxobroko.com.
  2. Go to Storage → select the pool.
  3. Open the Scrub tab (or Periodic Scrub Tasks depending on UI version).
  4. Note the schedule — e.g. first Sunday of the month at 00:00.

If a schedule exists and last scrub passed, you usually do not need a manual run.

Run a manual scrub now

  1. Log in to TrueNAS.
  2. Storage → click the pool name.
  3. Open Scrub (or Scrub Pool action in the pool menu).
  4. Click Scrub Pool / Start Scrub.
  5. Confirm if prompted.

Monitor progress

  1. Stay on Storage → pool → Scrub tab, or check Tasks / Jobs in the UI.
  2. Watch percentage complete and estimated time.
  3. Status should end as Finished with 0 errors.

During scrub:

  • Jellyfin and SMB still work — may be slower.
  • Avoid starting huge new torrent imports if the NAS feels sluggish.

If the scrub reports errors

  1. Write down the error count and which vdev or disk is mentioned.
  2. Do not delete the pool.
  3. Go to Read SMART disk errors and identify the sick drive.
  4. If the pool shows DEGRADED, switch to When the pool is degraded.

Change the scrub schedule (optional)

  1. Storage → pool → Scrub → Edit schedule (or Tasks → Scrub Tasks).
  2. Pick a quiet time — e.g. weekly or monthly, 2–4 AM.
  3. Save.

Do not cancel scrubs repeatedly without reason

Stopping mid-scrub is safe for data but delays verification. Let it finish unless the NAS is unusably slow and you need temporary relief.