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Verify Data Transfer

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  • Use Cases
  • Tasks
  • Document Counts
  • Hash Comparison
  • Document Comparison
  • Migration Verifier
  • Learn More

When mongosync has fully committed, verify the successful transfer of your data before you switch your application to using the destination cluster. You can verify your data transfer using document counts, hash comparison, document comparison, or the Migration Verifier.

Use Cases

You should verify your data after every sync. This is important in cases where you plan to move your application load from the source to the destination cluster.

Verification methods:

  • Document Counts

  • Hash Comparison

  • Document Comparison

  • Migration Verifier

The specific method you use to verify your data depends on your application workload and the complexity of the data.

Tasks

Document Counts

The most basic method of verification is to compare the number of documents in each synced collection on the source cluster to the number on the destination cluster.

This method only verifies a successful sync when run against clusters with insert-only workloads.

For more information, see Verify with Document Counts.

Hash Comparison

You can verify sync by comparing MD5 hashes of collections synced from the source cluster to the destination cluster.

While hash comparison ensures that the destination cluster has received all changes from the source, the dbHash command locks the cluster, preventing additional writes until it completes.

Note

Hash comparison is not possible with sharded clusters. It also does not work for standalone servers and replica sets that use MongoDB 4.4 or earlier releases, since the document field order can vary.

For more information, see Verify with Hash Comparison.

Document Comparison

You can verify sync by comparing documents on the source and destination clusters. Write a script that queries collections on the source cluster and then checks that the document exists with the same values on the destination cluster.

Migration Verifier

Migration Verifier connects to the source and destination clusters and performs a series of verification checks, comparing documents, views, and indexes to confirm the sync was successful.

Important

Migration Verifier is an experimental and unsupported tool.

For installation instructions, see GitHub.

Unlike other verification methods, Migration Verifier can run concurrent with mongosync, checking documents on the destination cluster as they sync.

For more information, see Verify with Migration Verifier.

Learn More

For more information, see:

← Telemetry
Verify with Document Counts →

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