Skip to main content
NetApp Knowledge Base

How is SnapMirror lag time calculated

  1. Last updated
  2. Save as PDF
Views:
345
Visibility:
Public
Votes:
0
Category:
snapmirror
Specialty:
dp
Last Updated:

Applies to

  • ONTAP 9
  • SnapMirror

Answer

  • SnapMirror lag time is the difference between when the snapshot was created on the source and the system time on the destination.

Example:
ontap912::> snapmirror show -destination-path svm1_ontap912:test912 -fields exported-snapshot,lag-time
source-path           destination-path      exported-snapshot                                                            lag-time
--------------------- --------------------- ---------------------------------------------------------------------------- --------
svm1_ontap913:test913 svm1_ontap912:test912 snapmirror.2e3cb37b-64a9-11ed-b07f-005056959654_2150626516.2024-10-11_132941 957:4:52

ontap912::> date
Node      Date                     Time zone
--------- ------------------------ -------------------------
ontap912-01
          Wed Nov 20 10:32:58 2024 Japan 
ontap912-02
          Wed Nov 20 10:32:59 2024 Japan
2 entries were displayed.

            So  lag time (957:4:52) = Wed Nov 20 10:32:58 2024 - 2024-10-11_132941

  • There are additional factors that can affect lag, including 
    • The timestamp on the last successfully transferred snapshot
    • The system time on the destination
    • The amount of time needed to transfer the snapshot from the source to destination
    • The amount of time elapsed between the last snapmirror update and running snapmirror show
  • Example of how lag is calculated
    • A snapshot is created at 22:55
    • A scheduled SnapMirror update runs at 23:00
    • The transfer takes 15 minutes to complete
    • Lag time will be 20 minutes at the end of the transfer
      • How is that calculated? The difference between snapshot creation time and initiating the transfer is 5 minutes, plus 15 minutes for the transfer to complete.

Note: When examining lag time in SNAPMIRROR.XML via AutoSupport, two factors can increase lag time:

  1. the elapsed time since the last SnapMirror transfer
  2. the time required to collect each AutoSupport section.

For example, if there is a 20-minute lag time and AutoSupport is triggered at 00:00 but takes 20 minutes to generate SNAPMIRROR.XML, the lag time will reflect an additional 1 hour and 20 minutes, displaying as 1:40:00 (1 hour and 40 minutes).

Additional Information

Frequently Asked Questions (FAQ): SnapMirror Lag

 

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.