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How does the "schedule" parameter in an ONTAP 9 SnapMirror policy rule work?

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Applies to

  • ONTAP 9
  • SnapMirror
  • Long-Term Retention Snapshots

Answer

  • SnapMirror relationship updates are scheduled via the schedule parameter on the SnapMirror relationship itself as seen in snapmirror show -instance

ClusterDR::> snapmirror show -instance

            Source Path: svmSrc:volSrc
       Destination Path: svmDst:volDst
      Relationship Type: XDP
Relationship Group Type: none
    SnapMirror Schedule: daily

  • Alternatively, SnapMirrors can be scheduled via the -transfer-schedule-name parameter in the SnapMirror policy
  • SnapMirror policy rules has a separate schedule parameter that can be seen in snapmirror policy show -instance and is an option when creating or modifying a SnapMirror policy rule with snapmirror policy add-rule and snapmirror policy modify-rule
  • This article discusses the use of this schedule parameter

ClusterDR::> snapmirror policy show -policy CustomMirrorVault -instance

                    Vserver: ClusterDR
     SnapMirror Policy Name: CustomMirrorVault
     SnapMirror Policy Type: vault
               Policy Owner: cluster-admin
                Tries Limit: 8
          Transfer Priority: normal
  Ignore accesstime Enabled: false
    Transfer Restartability: always
Network Compression Enabled: false
            Create Snapshot: false
                    Comment: -
      Total Number of Rules: 2
                 Total Keep: 15
                      Rules:
SnapMirror Label              Keep Preserve Warn Schedule Prefix
----------------------------- ---- -------- ---- -------- ----------
 daily                          10 false       0 -        -
 weekly                          5 false       0 weekly   weekly

ClusterDR::> snapmirror policy add-rule ?
    -vserver                   Vserver Name
   [-policy]                   SnapMirror Policy Name
   [-snapmirror-label]         Snapshot Copy Label
   [-keep]                     Snapshot Copy Retention Count
  [[-preserve] {true|false}]   Snapshot Copy Preserve Enabled
  [ -warn <integer> ]          Warning Threshold Count
  [ -schedule ]                Snapshot Copy Creation Schedule
  [ -prefix ]                  Snapshot Copy Creation Prefix

  • This schedule parameter found in a SnapMirror policy rule is not a transfer schedule and will not trigger a SnapMirror update
  • Instead, this schedule controls a feature known as Long-Term Retention (LTR) Snapshots
  • LTR Snapshots create independent snapshot copies directly on a SnapMirror destination volume without having to create and transfer a corresponding Snapshot copy on the SnapMirror source volume
  • When a schedule is used in a SnapMirror policy rule assigned to a SnapMirror relationship, that rule will create snapshots on the SnapMirror destination volume when the schedule triggers. These rules will not transfer Snapshots from the source volume
Other considerations of Long-Term Retention Snapshots
  • Ensure the schedule configured for LTR Snapshots does not overlap with the actual transfer schedule of the SnapMirror
  • Long-Term Retention Snapshots are only supported if the destination volume is not also a source (cascade). LTR Snapshots can still be used on the last volume of a cascade
  • This feature is only available for use with vault and mirror-vault type SnapMirror policies
  • You must have at least one rule in your SnapMirror policy with no schedule parameter
  • The feature is not supported for FlexGroup & SnapMirror under Cloud Backup Service. It is also not supported for Consistency Group SnapMirror
  • Beginning in ONTAP 9.14.1, LTR Snapshots are supported in SnapLock for SnapVault configurations

 

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