Async replication pauses during backup operations

Async replication operations pause during backup, causing replication lag to accumulate until the backup completes. In clusters with async replication enabled, this leads to data inconsistency between nodes during the backup window.

Upgrade to Weaviate v1.26 or later which includes fix from PR #6820. Monitor weaviate_async_operation_running during backup operations to verify replication continues. Track weaviate_backup_store_to_backend_ms to understand backup duration and potential impact window.