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
• To manage which items are being synchronized:
  • Mirror Deletions
• To determine what is synchronized per object:
  • Preserve Object Last-Modified Date and Time
• To configure SyncEngine processes:
  • GCS Rate Limits

Complete these steps to set up migration from GCS to a VAST S3 bucket:

1. Ensure that the prerequisites are met.

2. Create a connector for Google Cloud Storage.

3. Create a connector for VAST S3.

4. Create a migration from the source GCS bucket to the destination VAST S3 bucket.

5. Start the migration.

   Note: This step is only required when the migration does not have periodic resynchronization enabled.

6. Monitor migration progress and completion.

7. If necessary, 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. 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 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=<path to JSON key 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=<VMS IP> \
  --username=admin \
  --password=<password> \
  --vip=<VAST S3 VIP> \
  --access-key=<S3 access key> \
  --secret-key=<S3 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 <name>                # Default: SYNCENGINE_USER
--s3-uid <UID>                      # Default: 270270270
--tenant-name <VAST tenant name>
--secure-s3={true|false}
--checksum-algorithm {CRC32C|CRC64NVME|SHA256}
--case-sensitive-bucket-names={true|false}
--read-timeout <seconds>
--client-connect-timeout <seconds>
--client-retries-max-attempts <count>
--client-retries-mode <adaptive|standard|legacy>
--ssl-cert-file <path to 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:
     • 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 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 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 <hours>}
--enable-deletes={true|false}
--src-last-modified-header=={true|false}
--batch-size <GB>
--batch-file-count <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=<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