Skip to main content
NetApp Knowledge Base

What is an example how SnapMirror lag time is calculated?

Last Updated:

Applies to

  • ONTAP 9
  • SnapMirror


  • Scenario 1   
    Source  Destination
    ControllerA:vol_1 ControllerB:vol_1_mir
  1. A scheduled update starts at 12:00pm
  2. A SnapMirror snapshot is created on the Source volume, and a transfer is started 
  3. The transfer takes 45 minutes to complete
  4. The time on the destination system is now 12:46pm
  5. The transfer completed 1 minute ago

If measured during step 5, the lag is 46 minutes, because:

  • 46 minutes have elapsed since the snapshot was created on the source
  • 46 minutes elapsed since the snapshot was successfully transferred to the destination
  • On the Destination, Lag is calculated by finding the difference between:
    • The snapshot creation timestamp
    • The time on the destination, based on the destination storage controller's clock 
    • If the time is not configured correctly on the destination or source, the lag time will be incorrect
  • Scenario 2
    Primary Secondary
    CIFS_SVM:vol_1 CIFS_DR:vol_1_dr
  1. Based on the snapshot policy on vol_1, a snapshot is created at 5pm
  2. The snapshot is created with the snapmirror-label sv_daily
  3. At 1 AM the following morning, a scheduled snapmirror update is triggered, configured to replicate any snapshot labeled sv_daily
  4. The transfer takes 30 minutes to complete

The lag in this scenario would be 8 hours 30 minutes, because:

  • At the time of the scheduled snapmirror update, eight hours had elapsed since the snapshot was created and labeled sv_daily
  • Transferring the snapshot from the source to the destination took 30 minutes


NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.
Scan to view the article on your device
  • Was this article helpful?