--- title: "Migrate from GCS to VAST S3" slug: "migrate-from-gcs-to-vast-s3-34" updated: 2026-10-24T13:46:11Z published: 2026-10-23T15:24:03Z canonical: "kb.vastdata.com/migrate-from-gcs-to-vast-s3-34" --- > ## Documentation Index > Fetch the complete documentation index at: https://kb.vastdata.com/llms.txt > Use this file to discover all available pages before exploring further. # Migrate from GCS to VAST S3 ## Overview The Google Cloud Storage (GCS) connector extracts files from a GCS bucket into an S3 bucket on a VAST cluster. SyncEngine authenticates with a Google Cloud service account, lists source prefixes, and copies object data to the destination bucket. The following capabilities are supported for migrations from GCS to VAST S3: - To determine when data synchronization occurs: - [Periodic Resync](/documentation/docs/migrate-from-gcs-to-vast-s3-34#periodic-resync) - To manage which items are being synchronized: - [Mirror Deletions](/documentation/docs/migrate-from-gcs-to-vast-s3-34#mirror-deletions) - To determine what is synchronized per object: - [Preserve Object Last-Modified Date and Time](/documentation/docs/migrate-from-gcs-to-vast-s3-34#preserve-object-lastmodified-date-and-time) - To configure SyncEngine processes: - [GCS Rate Limits](/documentation/docs/migrate-from-gcs-to-vast-s3-34#gcs-rate-limits) Complete these steps to set up migration from GCS to a VAST S3 bucket: 1. Ensure that the [prerequisites](/documentation/docs/migrate-from-gcs-to-vast-s3-34#before-you-begin) are met. 2. [Create](/documentation/docs/migrate-from-gcs-to-vast-s3-34#create-gcs-connector) a connector for Google Cloud Storage. 3. [Create](/documentation/docs/migrate-from-gcs-to-vast-s3-34#create-vast-s3-connector) a connector for VAST S3. 4. [Create](/documentation/docs/migrate-from-gcs-to-vast-s3-34#create-migration) a migration from the source GCS bucket to the destination VAST S3 bucket. 5. [Start](/documentation/docs/migrate-from-gcs-to-vast-s3-34#start-migration) the migration. > **Note**: This step is only required when the migration does not have periodic resynchronization enabled. 6. [Monitor](/documentation/docs/migrate-from-gcs-to-vast-s3-34#monitor-migration) migration progress and completion. 7. If necessary, [troubleshoot](/documentation/docs/migrate-from-gcs-to-vast-s3-34#troubleshoot). The following limitations apply: - A GCS bucket can only be migrated to a VAST S3 bucket. No other destination types are supported. - One source bucket is allowed per migration. If you need to migrate multiple buckets, multiple migrations are to be set up. ## Features ### Periodic Resync In addition to starting a migration once it is created, SyncEngine can be configured to automatically run a resynchronization at user-supplied intervals. - In SyncEngine UI, set the **SyncMode** to **Automatic** and enter an interval (in hours) in the **Sync Interval** field. - In SyncEngine CLI, include the `--sync-mode automatic=true` and `--sync-interval <interval>` options when submitting the `migration create` command. For migrations set to **Automatic** synchronization mode, the first synchronization starts immediately after the migration is created, and the subsequent synchronizations are performed periodically with the specified interval. A subsequent synchronization cannot be triggered manually. To be able to manually start a synchronization on demand, set **SyncMode** to **Manual**. ### Mirror Deletions You can determine how SyncEngine handles the items in the source store that have been deleted since the previous migration run. By default, SyncEngine does not delete such items from the destination. If you want to have them deleted, configure the migration to mirror source deletions at the destination: - In SyncEngine UI, select the **Mirror source deletions at destination** option when creating a migration. - In SyncEngine CLI, include the `--enable-deletes=true` option when submitting the `migration create` command. > **Note:** Deletion of items at the destination cannot be undone by disabling this setting. ### Preserve Object Last-Modified Date and Time When used with VAST Cluster 5.5.0 or later, SyncEngine can preserve the `Last-Modified` date and time of objects being migrated so that after the migration, this attribute still points to the last modification made by a user to the object in the source bucket. If this feature is disabled, the `Last-Modified` attribute is set to the date and time when the object was copied to the destination VAST S3 bucket. When migrating to a VAST cluster version prior to 5.5.0, the `Last-Modified` attribute cannot be preserved. Use the following options to enable or disable preserving of objects' `Last-Modified` date and time: - In SyncEngine UI, select or unselect the **Stamp source last-modified via request header** checkbox when creating a migration. - In SyncEngine CLI, include the `--src-last-modified-header={true|false}` option when submitting the `migration create` command. When preserving of source `Last-Modified` date and time is enabled and copying of S3 object tags is disabled, objects that have the same `Last-Modified` timestamp in source and destination buckets are skipped during automatic resynchronization, which helps improve performance. ### GCS Rate Limits You can set request rate limits to prevent SyncEngine from causing excessive load on the source GCS store: - Cap the overall number of requests (per second) that SyncEngine sends to the GCS API. - Restrict throughput when getting objects from the source GCS store. Each of the limits applies to the aggregate amount of requests or throughput by all workers used by the connector. Each limit is enforced independently of the other limit. On reaching a limit, workers wait and retry so that synchronization continues after the pause. By default, no request rate limits are set. Set rate limits if during a representative migration, vendor 429/503/SlowDown errors appear in the worker logs, and the Grafana **Connector Rate Limits** panel (or the Prometheus metrics `connector_rate_limit_waits_total{connector_id, axis}`) shows the wait counter growing. If no throttling and no vendor errors occur, you do not need to set rate limits. For recommended request rates for GCS, see [GCS documentation](https://docs.cloud.google.com/storage/docs/request-rate). Typically, no rate limiting is needed when migrating from GCS to VAST S3. To set GCS rate limits: - In SyncEngine UI, use the **API calls per second** and **Bytes per second** fields in the GCS connector settings. > **Note:** Connector rate limits can only be set in SyncEngine UI. Avoid configuring multiple connectors for the same Google Cloud service account with rate limits that, when combined, exceed the maximum allowed request rate for the GSC API. Use a single connector instead. ## Before You Begin Ensure that the prerequisites are met: ### GCS - A Google Cloud service account with *Storage Object View* permissions allowing to list and get objects from the source bucket. - A JSON key for the Google Cloud service account. You create a JSON key in your Google Cloud Console. - Source bucket name and, optionally, object prefix. ### VAST Cluster #### Networking - VAST cluster's management IP. - A DNS-resolvable name of the tenant's virtual IP pool to access the VAST S3 endpoint, or a virtual IPv4 address from that pool. - Network connectivity from workers to the destination VAST S3 endpoint. #### VAST Tenant and Admin Credentials - If your VAST cluster has multiple VAST tenant configured: - To migrate to one of the tenants: - The name of the VAST tenant where the destination VAST S3 bucket will reside - Username and password for the VAST tenant admin user - To migrate to the default tenant: - Username and password for the VAST cluster admin user - If your VAST cluster is not configured for multi-tenancy: - Username and password for the VAST cluster admin user #### Create User Create a user with S3 access keys allowing to create a bucket and put objects to it. 1. Create a local user on the VAST provider attached to the tenant where the destination VAST S3 bucket will reside. Ensure that the user has the *Allow Bucket Creation* option enabled. 2. Generate S3 access key for the user. 3. Create an identity policy to grant the user full access to the destination bucket (`"Action": "s3:*", "Effect": "Allow"`). 4. Assign the identity policy to the user. Note the username and UID of the created user. #### Create View Policy Create a view policy that will control access to the destination VAST S3 view. In the view policy: - Select the S3 Native security flavor. - Set Name length limit to Native Protocol Limit. - Set Allowed Characters to Native Protocol Limit. #### Create View Create an Element Store view exposing the destination VAST S3 bucket. In the view settings: - Select the S3 Bucket protocol. - Select the view policy you created. - Select the user you created as the bucket owner. ### SyncEngine - The SyncEngine control plane and at least one worker are up and running. - At least one worker label of a deployed worker is known. (The worker label is set when you deploy the worker.) ## Create GCS Connector A GCS connector is used to connect to the GCS where data to be migrated resides. ### SyncEngine UI 1. In the **Connectors** page, click **New Connector**. A wizard dialog appears to walk you through the connector creation steps. 2. In the **Type & name** step: - Select the **GCS** connector type. - In the **Connector name** field, enter a unique name for the connector. The name can contain up to 63 characters, including uppercase and lowercase English letters, digits, periods (.), hyphens (-) and underscores (_). 3. In the **Configure** step, paste the contents of the JSON key file associated with your GCS service account. 4. In the **Rate limits** step, set optional [request rate limits](/documentation/docs/migrate-from-gcs-to-vast-s3-34#gcs-rate-limits) for the connector: | Field | Description | | --- | --- | | **API calls per second** | Maximum allowed number of API calls per second. Leave blank for unlimited (default). | | **Bytes per second** | Maximum allowed download throughput. Leave blank for unlimited (default). | 5. In the **Review** step, review the settings you've made. If you want to make changes, click **Back**. Otherwise, click **Create Connector**. The connector is created and displayed in the **Connectors** page. ### SyncEngine CLI The following command creates a GCS connector named `src-gcs`: ``` syncengine-cli connector create \ --type=gcs \ --name=src-gcs \ --service-account-file= ``` > **Note:** Connector rate limits can only be set in SyncEngine UI. The output should be similar to the following: ``` Successfully created connector 'src-gcs' with ID 15 ``` > **Tip:** Note the connector ID in the output. ## Create VAST S3 Connector A VAST S3 connector is used to connect to the VAST S3 server on the VAST cluster to which you want to migrate the data. ### SyncEngine UI 1. In the **Connectors** page, click **New Connector**. A wizard dialog appears to walk you through the connector creation steps. 2. In the **Type & name** step: - Select the **Vast S3** connector type. - In the **Connector name** field, enter a unique name for the connector. The name can contain up to 63 characters, including uppercase and lowercase English letters, digits, periods (.), hyphens (-) and underscores (_). 3. In the **VMS cluster** step, enter VAST cluster's VMS IP and admin credentials: | Field | Description | | --- | --- | | **Management IP** | VAST cluster's management IPv4 address or DNS-resolvable hostname (up to 253 characters). | | **Username** and **Password** | Username and password to log in to the VMS. If the destination bucket is on one of VAST cluster tenants, enter credentials of the admin user for that tenant. If the destination bucket is on the default tenant, enter credentials of the VAST cluster admin user. | | **Tenant name** | The name of the VAST cluster tenant where the destination bucket resides. If not specified, the default tenant is used. | 4. In the **S3 endpoint** step, configure an S3 endpoint on the VAST cluster. | Field | Description | | --- | --- | | **VIP** | A DNS-resolvable name of the tenant's virtual IP pool to access the VAST S3 endpoint, or a virtual IPv4 address from that pool. A DNS-resolvable name is recommended. | | **Access Key** | Enter the S3 access key for the bucket owner user. | | **Secret Key** | Enter the private key for the bucket owner user. | | **S3 Username** | Enter the username for the bucket owner user. | | **S3 UID** | The UID of the bucket owner user. | | **Endpoint URL** | The URL to access the S3 endpoint. This field is optional. If not specified, the URL is derived from the **VIP** field. | | **Use secure S3 connection (HTTPS)** | Select to use HTTPS. If selected, you'll need to provide a TLS certificate in a next step. If not selected (default), HTTP is used. | 5. In the **Bucket & advanced** step, optionally configure advanced settings for the destination S3 bucket: | Field | Description | | --- | --- | | **Case-sensitive bucket names** | When enabled, SyncEngine allows for bucket names that contain both lowercase and uppercase characters. | | **Checksum Algorithm** | Checksum algorithm for S3 PUT operations: `CRC32C` (default), `CRC64NVME` or `SHA256`. Note that `CRC64NVME` and `SHA256` require VAST Cluster 5.5.0 or later. SyncEngine will verify if your VAST cluster supports checksum verification for the selected algorithm. | | **Read Timeout** | Socket read timeout, in seconds. Valid values: 60–3600. Default is 300. | | **Connect Timeout** | S3 endpoint connection timeout, in seconds. Valid values: 5–300. Default is 60. | | **Max Retries** | The maximum allowed number of retries by the VAST S3 client. Valid values: 1–100. Default is 3. | | **Retry Mode** | Select one of VAST S3 client retry modes: **Adaptive** (default) for rate-limiting of requests when throttled, **Standard** for exponential backoff with jitter, **Legacy** for simple exponential backoff. | 6. In the **Rate limits** step, leave the defaults unchanged ('0', no limits set). These fields are reserved for future use. 7. In the **SSL** step, use the **SSL Certificate Content** field to enter the TLS certificate (in PEM format) to secure the S3 connection. If left blank, default CA certificates are used. 8. In the **Review** step, review the settings you've made. If you want to make changes, click **Back**. Otherwise, click **Create Connector**. The connector is created and displayed in the **Connectors** page. ### SyncEngine CLI The following command creates a destination VAST S3 connector named `dest-vast-s3` to connect to the S3 endpoint at `<VAST S3 VIP>` on a VAST cluster with a management IP of `<VMS IP>`: ``` syncengine-cli connector create \ --type=vast_s3 \ --name=dest-vast-s3 \ --mgmt-ip= \ --username=admin \ --password= \ --vip= \ --access-key= \ --secret-key= ``` > **Note:** To auto-generate S3 access keys, omit the `--access-key` and `--secret-key` options from the command. Optional flags when creating a connector of the `vast_s3` type: ``` --s3-username # Default: SYNCENGINE_USER --s3-uid # Default: 270270270 --tenant-name --secure-s3={true|false} --checksum-algorithm {CRC32C|CRC64NVME|SHA256} --case-sensitive-bucket-names={true|false} --read-timeout --client-connect-timeout --client-retries-max-attempts --client-retries-mode --ssl-cert-file ``` The output should be similar to the following: ``` Successfully created connector 'dest-vast-s3' with ID 37 ``` > **Tip:** Note the connector ID in the output. ## Create Migration Create a migration to move the data from your source GCS store to an S3 bucket on the VAST cluster. ### SyncEngine UI 1. In the **Migrations** page, click **New Migration**. A wizard dialog appears to walk you through the migration creation steps. 2. In the **Source** step, select the Google Cloud Storage connector that will be used to connect to the source S3 store. 3. In the **Destination** step, select the VAST S3 connector that will be used to connect to the destination VAST cluster. 4. In the **Paths** step: - Under **Migration Label**, specify a SyncEngine worker label for the migration. The label is used to route migration jobs to the appropriate SyncEngine worker. One worker can be associated with one or more migration labels. Workers deployed with a certain label handle jobs for all migrations that have that label. You can create a new label or use an existing one. - To create a new label, select **Create new label** and enter a text string in the **New Label** field. The label can contain up to 128 characters, including uppercase and lowercase English letters, digits, periods (.), hyphens (-) and underscores (_). - To use an existing label, select **Use existing label** and enter the label string in the **Existing Label** field. - Under **Paths**, specify the paths to the migration source and destination. - Under **Source**, enter the source bucket name and, optionally, an object key prefix (used to migrate only objects with the prefix specified), for example: `bucket-name/object-prefix/`. - In the **Destination**, enter a name for the destination S3 bucket on the VAST cluster and, optionally, an object key prefix to be assigned to the migrated objects. If an object prefix is specified, also include the trailing slash. If you specify the bucket name only, no trailing slash is needed. 5. In the **Sync mode** step: - Under **Sync Mode**, specify if you want to run the migration once or [periodically](/documentation/docs/migrate-from-gcs-to-vast-s3-34#periodic-resync): - To run the migration once, select **Manual** in the **SyncMode** field. Migration will be started after you submit the migration job manually. - To run the migration automatically at certain intervals, select **Automatic** in the **Sync Mode** field and enter an interval (in hours) in the **Sync Interval** field. The default interval is 24 hours. 6. In the **What you're copying** step: - Under **What you're copying**: - Review the settings you've made. If necessary, click **Back** and change as needed. - Under **S3 object metadata**: - Optionally select **Stamp source last-modified via request header** to [preserve](/documentation/docs/migrate-from-gcs-to-vast-s3-34#preserve-object-lastmodified-date-and-time) the objects' original last-modified data and time during the migration. > **Note:** This option requires VAST Cluster 5.5.0 or later. - Under **Delete propagation**: - Decide how SyncEngine [handles the objects that have been deleted](/documentation/docs/migrate-from-gcs-to-vast-s3-34#mirror-deletions) since the previous migration run. By default, SyncEngine does not delete such objects from the destination S3 bucket. If you want to have them deleted, select **Mirror source deletions on the destination**. 7. In the **Batch sizing** step, optionally adjust the size of batches that SyncEngine uses when copying the data. By default (if no values are entered in the fields provided), SyncEngine uses VAST cluster's defaults which are suitable for most workloads. - In the **Batch size** field, specify the maximum allowed batch size in GB. If not specified, a default of 1GB is used. - In the **Batch file count** field, specify the maximum allowed number of objects per batch. If not specified, a default of 1000 objects is used. 8. In the **Per-task timeouts** step, optionally configure suitable timeouts for the migration jobs. 9. In the **Review** step, review the settings you've made. If you want to make changes, click **Back**. Otherwise, click **Create Migration**. The migration is created and displayed in the **Migration** page. ### SyncEngine CLI The following commands creates a migration of objects prefixed with `/archive/` from GCS bucket `my-gcs-bucket` to a VAST S3 bucket named `gcs-data-dest`. The migration is to be accomplished by workers labeled with `MYFIRSTMIGRATION` using connectors with connector IDs `3` and `4`. ``` syncengine-cli migration create \ --source-connector-id=3 \ --destination-connector-id=4 \ --source-bucket=my-gcs-bucket/archive/ \ --destination-bucket=gcs-data-dest \ --label=MYFIRSTMIGRATION ``` Optional flags: ``` --sync-mode {manual | automatic --sync-interval } --enable-deletes={true|false} --src-last-modified-header=={true|false} --batch-size --batch-file-count ``` The CLI creates a migration and displays its properties. The output should be similar to the following: ``` Creating migration: MYFIRSTMIGRATION Source type: gcs Destination type: vast_s3 Source: my-gcs-bucket/archive/ Destination: gcs-data-dest Migration created successfully! ID: 2 Label: MYFIRSTMIGRATION Sync Mode: manual File Deletions: Disabled ``` > **Tip:** Note the migration ID in the output. ## Start Migration Manual migration start is only relevant for migrations that do not have periodic resynchronization configured. For migrations with periodic resynchronization, the migration starts automatically upon creation. ### SyncEngine UI Navigate to the ​**Migrations**​​ page and click the start button for the migration you want. ### SyncEngine CLI Run the command: ​ syncengine-cli migration start --migration-id=
​
The output should be similar to the following:
​
Starting sync job for migration: MYFIRSTMIGRATION
✓ Sync job created successfully!
Job ID: 2
Status: pending ## Monitor Migration As the migration progresses, its status changes as follows: `Not Started` (or `init`) -> `Waiting for Worker` (or `pending`) -> `Syncing` -> `Synced`. When complete, the destination S3 bucket will have objects migrated from the source bucket. ### SyncEngine UI Check the migration status in the **Migrations** page. ### SyncEngine CLI Run the command: ``` syncengine-cli migration status --migration-id= ``` The output should be similar to the following: ``` === Migration Status: MYFIRSTMIGRATION === ID: 33 Status: synced Source: my-source-bucket Destination: s3-data-dest Sync Mode: manual Last Sync: 2026-07-09 15:10:54 Settings: Error Retry: 0 Task Retry: 0 Batch Size: 0 GB Batch File Count: 0 Sync Jobs: 1 Recent Sync Jobs: +----+-----------+------------------+-------------+-------+------+ | ID | STATUS | START TIME | DURATION | FILES | SIZE | +----+-----------+------------------+-------------+-------+------+ | 95 | completed | 2026-07-09 15:10 | PT4.623401S | 1 | 29 B | +----+-----------+------------------+-------------+-------+------+ ``` ## Troubleshoot | Symptom | Likely Cause | Solution | | --- | --- | --- | | Sync job stays *pending* | Migration label does not match worker label | Update the migration to use the same label as the deployed worker. | | Sync fails writing to the VAST cluster | Invalid S3 credentials, or unreachable S3 virtual IP | Confirm access keys and S3 virtual IP reachability from workers. | | Authentication error at connector creation | Malformed JSON key of the Google Cloud service account | Verify that the specified JSON key file contains valid data. | | GCS returns HTTP error code `403` | GCS account has insufficient permissions on the source bucket. | Ensure that the GCS account has *Storage Object Viewer* permissions allowing to list and get objects from the source bucket. | | Connection timeout | Wrong endpoint, firewall, or virtual IP | Confirm URLs and ports 80/443 from workers. | | Objects missing after synchronization | Wrong bucket or prefix | Verify the source and destination paths specified for the migration. |