Data Domain: SAS Cable Configuration, Topology checks and Testing

PURPOSE

This article lists steps on how to ensure Serial Attached SCSI (SAS) cables are configured using the correct topology and that cable connectors are securely fastened and support the necessary data throughput.

• Ensure Correct Topology for Storage Configuration
• Ensure that Connectors are Securely Fastened
• Testing Cable Connections and Data Throughput

APPLIES TO

• Data Domain systems with External Storage 
• All Software Releases

If a SAS cable is faulty, the system can experience sluggishness which can lead to and report the following error conditions in the Autosupport and its alerting mechanism:

• Enclosure multipath path fails back to single path
• Alert: Duplicate WWN 50050cc1011820cf found in 3.B.?, Loop back to HBA port 4a
• Encl <enclosure id> (<enclosure serial #>) Disk <disk id> only has 1 active connection path and the required number is 2
• Disk <disk id> is absent and should be replaced
• Disk <disk id> is failed and should be replaced
• Disk <disk id> is unknown and should be replaced
• In an enclosure, multiple disks can be seen in an absent, failed, unknown state or even a known state
•  "se enclosure show detailed-status 2 displays"  Host or EXP N port link speed <12.0 Gbps on ES20 OR <24Gbps on ES30/DS60
•  "se enclosure show detailed-status 2 displays"  Host or EXP N port link speed 0 .0 Gbps (disconnected)
• Faulty Link Displays 9.0 Gbps (i.e. <12.0 Gbps on ES20 OR <24Gbps on ES30/DS60)

1. Verify that a SAS cable is connected and working properly. At the Command Prompt type:
    
   # enclosure show topology

   
   Confirm primary and secondary paths to each enclosure to be good without any question marks:
   
   
   
   A defective SAS cable shows question marks (???) between paths and the error message stating a problem has been detected.

   Port      enc.ctrl.port        enc.ctrl.port       enc.ctrl.port
   3a    >   5.A.H:5.A.E   ? ? ?  7.B.H:7.B.E    >    6.B.H:6.B.E
   
   Error message: ? - A possible problem was detected for this shelf controller or the cable connected to it.
    

2. If question marks (?) are seen between paths, physically inspect the SAS cable connectivity between shelves. If all cables are snug and securely fastened, however, the alert has not cleared, further troubleshooting is required; Create a service request
   
    
3. If exclamation marks (!) are seen between paths, it indicates that a PHY error has been recorded. Contact support to assist in running diagnostics.

4. An Alert of Duplicate WWN can be caused by loose or defective cables, connecting an Expansion Port directly to the HBA (SAS Card) port (for example 6.B.E > 4a) or incorrect connections between enclosures in the daisy chain. Check all connections and verify that the cabling is in EMC/Data Domain best practices. Once fixed, a reboot mat be required to reset the chain.

• Data Domain: How to run SAS/Shelf Diagnostics
• Datadomain: Troubleshooting Adding a Shelf | Additional Storage/Enclosure
• Data Domain ES30 Expansion Shelf Hardware Guide
• Data Domain ES30 Expansion Shelf and FS15 SSD Shelf Hardware Guide
• Data Domain DS60 Shelf Expansion Hardware Guide