Data Domain: Failed, Absent, Unknown, or Powered-off Disk

Summary: This article describes how to resolve the condition where a disk drive is in a failed, absent, or powered off state.

This article applies to This article does not apply to This article is not tied to any specific product. Not all product versions are identified in this article.
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Symptoms

Alert | Symptom code:

  • Event Codes: STORAGE-00001, STORAGE-00002, PHYM-00001
  • Alert Messages:
    • Enclosure disk has failed and should be replaced
    • Disk has a hardware fault and may need to be replaced
    • Disk is absent and should be replaced
    • Unable to access the disk; disk state is powered off
    • A disk has failed, and the enclosure slot has been disabled

Affected Products:

  • All Data Domain systems
  • All Data Domain Operating System (DDOS) software releases

Cause

DDOS continuously monitors disk health and automatically fails a drive when critical I/O errors occur.

Alerts are generated when a disk is:

  • Removed (absent)
  • Dead or failed
  • Powered off (manually or automatically by DDOS to prevent backend issues)

Resolution

1. Verify and confirm the failure:

  • Verify the alerts on the system using DDMC, Data Domain System Manager (DDSM) Web UI, or DD-CLI (SSH).
    • DD-CLI # alerts show current
    • DDSM > Alerts 
  • Identify and confirm the current state of all drives in the system.
    • DD-CLI # disk show state | AND | # disk show hardware
    • DDSM > Hardware > Storage > Disks 

      • Disk state indicators:

        • F = Failed
        • R = Reconstructing
        • S = Spare
        • A = Absent
        • P = Powered-off

Example: DD-CLI:
# disk show state

sysadmin@DD# disk show state
Enclosure   Disk
             1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
---------   ----------------------------------------------
1            .  .  .
2            .  .  .  .  .  .  .  .  .  .  .  .  .  .  s
3            .  .  .  .  .  .  .  .  .  .  .  .  .  .  s
4            .  .  .  .  .  F  .  .  .  .  .  .  .  .  R
---------   ----------------------------------------------

Here notice that disk 4.6 (F)ailed - (R)econstructing to Spare disk 4.15.

For DD3300 disk issues, consider this article Data Domain: DD3300 Mapping disk alerts to the correct hard drive slot

2. Raise a Service Request (SR)

  • Replace single failed disks as soon as possible.
  • If an SR was not automatically generated over dial home:
    • Contact your support provider and raise an SR.
  • If multiple disk failures are present:
    • Contact Dell ProSupport (or your contracted Service Provider) immediately for guidance.

3. Monitor the System While Waiting for Replacement Disk.

After raising an SR, continue monitoring to ensure system stability.

3.1 Understand why backups continue.

    • Data Domain systems use RAID 6 (double parity).
    • The system protects data during disk failure.
    • DDOS reconstructs data automatically onto an available spare.
    • Backup and restore operations continue during reconstruction.

3.2 Verify reconstruction status.

    • Run: 
      disk show state
    • Confirm a disk shows (R)econstructing.

3.3 Monitor reconstruction progress

    • Re-run disk show state periodically.
    • Reconstruction time depends on disk size and system load.

3.4 Watch for additional disk failures.

    • ⚠️ Critical Warning
      RAID 6 tolerates two disk failures per disk group.
      A second failure during reconstruction increases the risk.

    • If another disk failure occurs:

      • Contact Dell ProSupport (or your contracted Service Provider) immediately.

3.5 Identify the physical disk

    • Disk format: Enclosure.Slot (example: 2.27)
    • In DDSM:
      • Navigate to Hardware > Storage > Disks
      • Select disk → click Beacon to enable LED
    • In DD-CLI:
      • # disk beacon n.n

3.6 Do not remove the failed disk.

    • Leave the failed disk installed until the replacement arrives.
    • Early removal provides no benefit and may complicate tracking.

4. Replace the failed disk:

  • Follow the official disk replacement procedures in Data Domain Documentation

    • Best Practice:

      • Wait 2 minutes between removal and insertion:

        1. Remove failed disk
        2. Wait 2 minutes
        3. Insert replacement disk

      • This allows the controller to properly unregister the old disk and prevents hot-plug recognition issues.

5. Verify Post-Replacement Status:

From DD-CLI # disk show state

    • DDSM > Hardware > Storage > Disks 

Example: DD-CLI:

    • sysadmin@DD# disk show state
Enclosure   Disk
             1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
---------   ----------------------------------------------
1            .  .  .
2            .  .  .  .  .  .  .  .  .  .  .  .  .  .  s
3            .  .  .  .  .  .  .  .  .  .  .  .  .  .  s
4            .  .  .  .  .  s  .  .  .  .  .  .  .  .  .
---------   ----------------------------------------------
  • The replacement disk becomes Spare, and the reconstructed disk returns to active use.

6. Troubleshoot Replacement Issues.

If the new disk shows as Unknown:

    1. Run command # disk rescan
    2. Verify status of disk from DD-CLI # disk show state

If the new disk reports as failed

    1. Run command # disk rescan
    2. Verify status of drive from DD-CLI # disk show state
    3. If still (F)ailed, run this command from DD-CLI: # disk unfail <encl.disc>

For example: # disk unfail 5.6

If the disk status is confirmed OK (In-use or Spare), clear any related alerts:

    1. From DD-CLI # alerts clear alert-id <alert-id>

    Additional Information

    Reference:

    Videos

    PowerProtect DD - Replacing Cache Tier Disk on DD6900/DD9400

    Duration: 00:02:09 (hh:mm:ss)
    Closed captions: None available


    PowerProtect DD - Replacing Cache Tier Disk on DD9900

    Duration: 00:02:13 (hh:mm:ss)
    Closed captions: None available

    Affected Products

    Data Domain
    Article Properties
    Article Number: 000043773
    Article Type: Solution
    Last Modified: 30 Jun 2026
    Version:  17
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