A sync-server replacement succeeds only if object identity stays stable.

Before a new Entra Connect server is introduced, document source anchor choices, filtering rules, OU scope, custom sync rules, export settings, and every exception that the old server quietly carried.

Runbook note: Do not retire the existing sync server until the staging server has produced identical connector-space behavior and you have verified object joins for representative users, groups, and devices.

• Capture connector configuration, sync schedule behavior, custom rule sets, and attribute flows that differ from default deployments.
• Document immutable ID or source anchor behavior for cloud-joined users, service accounts, groups, and hybrid devices.
• Review service-account permissions, TLS inspection, proxy settings, and firewall egress rules needed by the sync engine.
• Define rollback as preserving the original active server with exports disabled on the replacement until parity is proven.

Command path:

• Get-ADSyncScheduler
• Get-ADSyncConnectorRunStatus
• Get-ADSyncGlobalSettings
• Get-Service ADSync

GUI path: Microsoft Entra Connect Sync Service Manager, Synchronization Rules Editor, and the Entra Connect wizard on the current server.

The new server should observe and compare before it exports.

Install the replacement with the same version and connector intent where possible, enable staging mode, and let it import and synchronize until differences are explained instead of assumed away.

• Match prerequisite software, service-account model, and network reachability before installation so configuration drift does not hide as sync drift.
• Enable staging mode during setup so the replacement processes imports and syncs without writing to Microsoft Entra ID.
• Recreate or import custom sync rules carefully and validate precedence against the existing production server.
• Allow several full sync cycles to complete so slow-moving or edge-scope objects surface before cutover.

Command path:

• Start-ADSyncSyncCycle -PolicyType Initial
• Get-ADSyncScheduler
• Get-EventLog -LogName Application -Source "Directory Synchronization" -Newest 50

GUI path: Microsoft Entra Connect setup wizard > Customize synchronization options > Enable staging mode.

Parity matters more than a clean installer finish.

The replacement is ready only when imports, joins, exports, and error counts line up with the current server for the same object populations and edge cases.

• Compare representative users, groups, contacts, and devices in connector space on both servers to confirm matching anchor and join logic.
• Resolve any duplicates, soft-match surprises, or filtered objects before the new server is allowed to export.
• Test password-hash sync or pass-through auth dependencies if they are part of the deployment.
• Confirm scheduler behavior, run durations, and operational alerting are equivalent to the current service.

Command path:

• Get-ADSyncRunProfile
• Start-ADSyncSyncCycle -PolicyType Delta
• Get-ADSyncExportDeletionThreshold

GUI path: Synchronization Service Manager > Connectors, Connector Space, Metaverse Search, and Operations tabs.

Make one server authoritative and leave the other ready to resume if needed.

Cutover is the moment staging mode flips and active export responsibility changes. Keep that move small, reversible, and fully observed.

• Put the old server into staging mode or stop its scheduler before activating exports on the new server.
• Trigger an observed delta cycle and confirm expected exports, no unexpected deletions, and healthy completion states.
• Validate cloud sign-in, group updates, device writeback or password writeback if used, and representative object modifications after the flip.
• Retain the former server in a recoverable state until several successful production cycles have completed.

Command path:

• Set-ADSyncScheduler -SyncCycleEnabled $false
• Start-ADSyncSyncCycle -PolicyType Delta
• Get-ADSyncScheduler

GUI path: Microsoft Entra Connect wizard and Synchronization Service Manager during the staging-to-active transition.