Data Domain: SAS or MPATH Alerts

Applies to:

• All Data Domain (DD) models with External Storage attached
• All Data Domain Operating System (DDOS) versions

Each DD system maintains two SAS paths to every enclosure and its disks. A typical data path includes:

• PCIe SAS HBA → SAS HBA Port → SAS Cable → Enclosure Controller (LCC) → Disk

Failure at any point in this path can trigger alerts or event IDs. While alerts may indicate the fault, further investigation is often required.

Common SAS and MPATH Events:

EVT-MPATH-00003: Missing disk connection from system port Nx
EVT-MPATH-00005: Enclosure Disk only has active connection(s); required number is 2
EVT-MPATH-00006: Path redundancy to an enclosure is lost
EVT-SAS-03801: Enclosure cables on port have been connected incorrectly
EVT-SAS-03802: The HBA port is disabled
EVT-SAS-03803: The SAS HBA in slot has failed

Common causes of SAS or Multipath events are:

• Incorrect cabling or topology
• Site maintenance or upgrades (such as adding or upgrading storage, power maintenance, accidental cable disconnection)
• Loose or improperly seated SAS cables
• Faulty hardware (HBA, SAS cable, LCC, or disk)
• Transient firmware or software faults

Always restore full SAS multipath connectivity. Do not leave missing or degraded paths unresolved.

Recommended Actions:

1. Run Diagnostic Commands (to identify where the fault lies):

alerts show current
disk port show summary
disk port show stats
enclosure show topology
enclosure show controllers <n>
disk multipath status
disk rescan <n.n> (where n.n is the Enclosure.Slot reference)

2. Compare with previous Autosupport:

• Use a preevent Autosupport to identify missing or degraded connections.

3. Physical Inspection:

• Disable the file system (filesys disable) before reseating or moving any SAS cables.
• Check SAS and power cables for secure connections.
• Look for missing LEDs or fault indicators on controllers.

4. Reference Documentation:

• Consult Shelf Hardware Guides for cabling topology and best practices.

5. Escalation:

• If further assistance is needed, generate a Support Bundle and raise a Service Request with your contracted Support Provider.