CONTAP-735654: Asnyc SnapMirror fan-out lag increases while SnapMirror active sync (SMas) is resyncing
Issue
- Consider a scenario where clusters A, B, and C are in a SnapMirror fan-out configuration and A -> C is a SnapMirror active sync (SMas) relationship and A -> C is an asynchronous volume-level SnapMirror relationship.
- If the A -> B SMas relationship goes out of sync and then starts resyncing, the A -> C asynchronous fan-out may perform a scheduled update during the SMas resync transfer.
- The A -> C asynchronous fan-out update may fail to replicate a new Snapshot while the SMas is resyncing. This results in a higher lag time and potential RPO miss for the asynchronous fan-out.
- The following may be seen in the SnapMirror Audit logs on cluster C:
Mon Jun 29 18:00:00 UTC 2026 ScheduledUpdate[Jun 29 18:50:00]:f739240a-6d76-11f1-8320-d039eaca4700 Operation-Uuid=893babf3-3176-4424-9252-9444f8b18175 Group=none Operation-Cookie=0 action=Info No new Snapshot copy to transfer from source svmSrc:volSrc.
Mon Jun 29 18:00:00 UTC 2026 ScheduledUpdate[Jun 29 18:50:00]:f739240a-6d76-11f1-8320-d039eaca4700 Operation-Uuid=893babf3-3176-4424-9252-9444f8b18175 Group=none Operation-Cookie=0 action=End source=svmSrc:volSrc destination=svmDst:volDst status=Success bytes_transferred=0 network_compression_ratio=1.0:1- The source (cluster A) may report the following event log
Mon Jun 29 18:00:00 +0000 [ClusterA-01: repl_Handle_sync_control: sms.snap.not.replicated:notice]: Snapshot 'snapmirror.snapshot' is not sucessfully replicated for the relationship 'relationship_UUID' with source volume DSID 'dsid' and path '/vol/volSrc'. Reason: Failed while draining or blocking inflight I/O.