Dell EMC Unity : Backup and Test IP address is intermittently unreachable during async replication refresh (Customer Correctable)

Summary: Accessing Backup IP address over NFS can have stale nfs file handle during replication refresh/syncs.

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Symptoms



  • A customer is seeing packet loss on 'Backup And Test' IP address configured on AsyncReplication-target Unity side.
  • This IP is used for NFS ReadWrite snap access for business continuity operation or otherwise DR testing.
  • NFS mounted filesystem may exhibit 'stale NFS file handle" Error messages on the NFS client system or:

2020-05-05T00:59:58.411199-04:00 system kernel: nfs: server 10.10.10.100 not responding, still trying
2020-05-05T01:01:37.739207-04:00 system kernel: nfs: server 10.10.10.100 not responding, still trying
2020-05-05T01:04:53.067225-04:00 system kernel: nfs: server 10.10.10.100 not responding, still trying

Cause

The packet loss / stale nfs file handle during async replication refresh on the target resource nas-server is a code related problem.

Resolution

Workaround :
  • For SMB operations , proxy-nas setup allows RW operations in OE 5.x 
  • For NFS operations , proxy-nas setup can be used for Read Only.
  • For NFS RW operations , Customers might be able to avoid the problem entirely by temporarily pausing the nas-server (and filesystems) before taking a test. Alternatively,  RPO can be set to manual or a larger time frame to cover the duration of the test (so in essence no syncs will come through while the DR Testing is in progress)
Permanent fix is expected on the next Unity OE 5.1

Additional Information

Similarly , NDMP backup can fail on the DR as explained on the following KBA:

Dell EMC Unity: NDMP backup of destination async replication file systems may fail if File System Refresh occurs on Source side (Dell EMC Correctable)   


Relevant proxy-nas articles:

Dell EMC Unity: How to use Proxy NAS Server CIFS/NFS Access to replicated Snaps (User Correctable)   
Dell EMC Unity: How to configure proxy NAS servers on replication destination side (User Correctable)   


Data content check using the backup and test IP address :

Dell EMC Unity: How To How to perform Target Replication Data Content Check (User Correctable)

Dell EMC Unity: How to perform CIFS Target Replication Data Content (User Correctable)   

Note: Only registered Dell Customers can access the content on the above links.

Affected Products

Dell EMC Unity 500

Products

Dell EMC Unity 500
Article Properties
Article Number: 000082033
Article Type: Solution
Last Modified: 30 May 2024
Version:  3
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