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Object count delta between src and dst bucket within a Snapmirror-S3 relationship

Last Updated:

Applies to

  • Snapmirror-S3 (FabricLink)
  • ONTAP_S3 object store bucket


  • Within a Snapmirror-S3 FabricLink relationship with RPO=0, the destination object-store bucket object-count keeps on raising, possibly way above the object-count of the source bucket.
  • Aggregate hosting the affected bucket keeps on filling and space is getting tight or aggregate runs out of space.
  • Alternatively, in a lighter form, the object-count between source- and destination-bucket within the Snapmirror-S3 relationship, shows only different numbers with no outstanding work:

::> vserver object-store-server bucket show -fields object-count
vserver bucket     object-count
------- ---------- ------------
svm_dst bucket-dst 124080
svm_src bucket-src 124078
2 entries were displayed.

::> snapmirror show
Source            Destination Mirror  Relationship   Total             Last
Path        Type  Path        State   Status         Progress  Healthy Updated
----------- ---- ------------ ------- -------------- --------- ------- --------
            XDP  svm_dst:/bucket/bucket-dst
                                      Idle           -         true    -

::*> snapmirror show -instance
                            Source Path: svm_src:/bucket/bucket-src
                       Destination Path: svm_dst:/bucket/bucket-dst
                      Relationship Type: XDP
                 SnapMirror Policy Type: continuous
                      SnapMirror Policy: Continuous
                      Throttle (KB/sec): unlimited
                           Mirror State: Snapmirrored
                    Relationship Status: Idle
                        Relationship ID: 16d619e6-9044-11ed-823e-005056bbfb01
                 FabricLink Source Role: bucket-src
               FabricLink Source Bucket: active-mirror
                   FabricLink Peer Role: bucket-dst
                 FabricLink Peer Bucket: active-mirror
                    FabricLink Topology: 145c48be-9044-11ed-8707-005056bbcabb
             FabricLink Pull Byte Count: 0
             FabricLink Push Byte Count: 0
          FabricLink Pending Work Count: 0
                      FabricLink Status: ok

  • After manual deletion of all objects within the source-bucket, the object-count either on source-bucket, or on destination-bucket, or on both, does not drop down to zero and some or even the majority of occupied space is not released.
  • Deeper investigation shows, partial multipart-objects are left within the destination bucket when checking from an external S3 client like aws cli:

$ aws --profile bucket-dst --endpoint-url https://ontap_s3.local  s3api list-multipart-uploads --bucket bucket-dst --output text
UPLOADS 2023-01-09T09:57:09.000Z        f001    MjE1NTI5NTY5OF8xMDU2XzIzMF80NjgzNzU4Mg
UPLOADS 2023-01-09T10:03:46.000Z        f002    MjE1NTI5NTY5N18xMDU1XzE3MV80NjQzNTk2MQ

Note: If the destination-bucket had ever been promoted (Snapmirror-S3 was reversed), partial multipart objects can remain in both, source- and destination-bucket.

  • At the time when the Snapmirror-S3 relationship was initialized, air.repaired.vplus:notice events are reported within ONTAP event log show (EMS) output:
Thu Sep 15 09:07:09 +0200 [zbghns4-03: wafl_exempt07: air.repaired.vplus:notice]: AIR vplus rebuild of 1204~0.147527 completed for subtype 6

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