Issue

Migrating data from Google Vault to the Microsoft 365 Purview environment while ensuring no data loss and maintaining the same functional capabilities previously guaranteed by Google Vault (with the copmlement of Exterro).

This is due to the decommissioning of Google services and Google Vault in order to leverage the capabilities of Microsoft 365.

Recommendation

Option 3: Extract Google Vault data to a secure repository (GCP) + use Purview for active & new legal holds + retire Exterro

Background & Context

Historically, the legal and compliance departments have relied on a combination of Google Vault for native data retention and Exterro as the primary orchestration layer for managing legal holds and complex discovery workflows. However, as part of the broader infrastructure modernization and per the directive from the CISO Office, the Exterro platform is being phased out alongside Google services.

This shift necessitates a full transition to Microsoft Purview, which now serves as the centralized environment for information governance. The transition is not merely a technical migration of mailboxes and files, but a fundamental change in how the organization meets its statutory and litigation-related obligations.

For data move please refer to article LM01_KDD021 - GAM to support migration (GVault / Deleted Users / Talarian): https://wiki.syensqo.com/x/iDIzOg

Coexistence Period

During the migration from Google Workspace to Microsoft 365, "Legal Hold Subjects" will be managed in a split-governance model to ensure no data is lost during the transition.

The Strategy

• Microsoft Purview: Governs migrated Mailboxes and OneDrive (formerly MyDrive) files. Holds are applied here immediately upon migration.

• Google Vault: Governs Google Chat and any legacy data not yet decommissioned. Users must remain on hold in Vault until Google services are fully disabled.

Deleted User Data: GCP Cold Storage

To reduce licensing costs while maintaining compliance, data for deleted users will be transfered to a Google Cloud Platform (GCP).

1. Before a Google account is deleted, a full export of Vault data is performed.

   1. This data is moved to a GCP Archive bucket.

      1. Retention: All exported data is subject to a strict 5-year retention policy to meet regulatory requirements.

         1. After 5 years, the GCP lifecycle policy will automatically purge the data unless a manual legal extension is applied.

Operational Impact:

Storing deleted users' data in GCP while retaining new information in Microsoft 365 creates a fragmented discovery environment, complicating workflows for the Legal team.

Assumptions

• Secure Staging: The GCP storage will serve as a secure, high-capacity staging area where data integrity (hashing) is verified before ingestion into M365.

• Chain of Custody: The migration process will preserve all essential metadata (dates, authors, recipients) to ensure the data remains legally defensible.

• Tooling & Connectivity: The VM will be equipped with necessary migration tools and sufficient network bandwidth to handle large-scale data transfers between Google and Microsoft.

• Formatting Parity: Google-native files (Docs, Sheets) will be successfully converted to Microsoft-compatible formats during the VM staging phase to allow for full indexing by Purview.

• Capacity: The destination Microsoft 365 environment has been provisioned with adequate storage to accommodate the total volume of legacy data from Google Vault.

Constraints

• Migration of data from Gvault will be a process that may take up to 4–5 weeks.
• The migration can start only after the project completes the “Coexistence” phase. Users must no longer be able to continue using GWS, because for the migration a set of closed/static data is required. 
• During coexistence, data keeps changing/being overwritten, which prevents the migration.
• Migration possible early October 2026.

Impacts

• Lower long-term risk through structured migration: Moving Google Vault data to a secured repository and then closing Vault can simplify the legacy footprint—provided holds/retention and chain-of-custody documentation are recreated—making compliance posture clearer over time.
• Exported Vault data may be harder to search/use in Purview (format/metadata/indexing gaps)
• Manageable change with short transition phase: Expect a temporary ramp-up (training, updated procedures, initial validation), but day-to-day operations should stabilize quickly once Purview processes and access to legacy data are validated.

Retention Policy

Options considered

Option 1: Maintain Google Vault for legacy data + Purview for new cases + Exterro (notifications only)

• keep Google Vault for legacy Google data (need to license all existing vaulted users active and inactive ~2200 x7$/user = 15400 yearly)
• Purview eDiscovery for new litigation on M365 : covered by E5 / F5
• reduce Exterro scope for litigation notification only (missing in eDiecovery) : cost to be defined

Option 2: Extract Google Vault data to secure repository (GCP) + Purview for new cases + Exterro (notifications only) 

• Extract GVault data into a secured place (to be defined) today using GCP project
• New Microsoft Purview (eDiscovery) for new litigation: covered by E5 / F5
• Reduce Exterro scope for litigation notification only (missing in eDiecovery): cost to be defined

Option 3: Extract Google Vault data to secure repository (GCP) + Purview for new cases + retire Exterro

• Extract GVault data into a secured place (to be defined) today using GCP project
• New Microsoft Purview (eDiscovery) for new litigation: covered by E5 / F5
• Stop Exterro and utilize (eDiscovery) functionality

Evaluation

The shift to Purview reduces architectural complexity and licensing costs, but moves the organization from a specialized "Legal-First" tool (Exterro) to a "Platform-First" tool.

The primary trade-off is the loss of Exterro’s robust Legal Hold Notification automation, which now requires a defined internal process within the Microsoft environment.

See also

The following section describes relevant documentation: