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SnapMirror Latency or Lag Is Growing

The destination is hours behind, transfers take too long, or the protection dashboard shows growing SnapMirror lag.

What ONTAP is telling you

Lag time is time since the newest destination-consistent recovery point, not network round-trip latency. Relationship status, health, last transfer timestamps, duration, size, and error text distinguish a missed schedule from an active slow transfer or failed transfer.

EMS reference snapmirror.*; inspect the relationship's last-transfer-error rather than assuming a cause.

How to confirm

snapmirror show -destination-path <svm:volume> -fields state,status,healthy,lag-time,last-transfer-end-timestamp,last-transfer-duration,last-transfer-size,last-transfer-error
snapmirror show-history -destination-path <svm:volume>
cluster peer show -instance
network interface show -role intercluster
network route show

Output shape: A relationship row should show state/status, healthy, lag-time, transfer timing/size, and any last error. History provides operation result and transfer details; peer and intercluster views establish the replication path.

The fix

Resolve the reported transfer or peer/network error first. If transfers succeed but cannot meet the recovery-point objective, verify schedule frequency and measured change rate/bandwidth before modifying policy or capacity. Do not resync a healthy relationship merely because lag is high.

How to prevent it

Alert on lag against the actual RPO, trend transfer size/duration, retain history, and re-evaluate schedules and intercluster bandwidth when workload change rate grows.

Sources and version relevance

Commands and claims are limited to material already represented in the Black Box archive. CLI links target the archived ONTAP 9.19.1 reference; fields and availability can differ by release. Check your ONTAP version and on-cluster command ? before production use.

Related Black Box pages: SnapMirror problems · SnapMirror reference · bandwidth estimator · all troubleshooting guides

Related advisory: none identified in the archive for this operational symptom.