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CONTAP-118215: IO disruption or high latency following SMas Planned Failover

  1. Last updated
    May 7, 2025
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Category:
ontap-9
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dp
Last Updated:
5/7/2025, 3:46:58 PM

Issue

In certain ONTAP systems employing SnapMirror active sync (SMas) feature, some SMas source consistency groups (CGs) and volumes may experience I/O disruptions following a planned failover operation on a different SMas relationship. This may also show up as sudden high latency in the range of 20 sec. 
Illustration
cg1_src              -----      cg1_dst

  • cg1_vol_src    -----      cg1_vol_dst

cg2_src              -----      cg2_dst
  • cg2_vol_src    -----      cg2_vol_dst

When snapmirror failover command is executed on cg1_dst, cg2_vol_src which belongs to cg2 can potentially face an IO disruption if cg1_vol_src and cg2_vol_src are located on the same node.
Volumes Affected
  • The defect is specific to SMas volumes and typically limited to a specific volume co-located with source endpoints of the CG undergoing planned failover.
  • Non-SMas volumes (for example, volumes in SM-S or SM-Async relationships) are not affected.

Symptoms
  • Hosts may notice high latency in reading or writing data — often a consistent latency of about 20 seconds.
  • Hosts may encounter other I/O disruptions or completely inaccessible LUNs associated with the consistency groups impacted.

 

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