docs(s3): add troubleshooting to veeam tutorial MTA-4808b (#3447)

* docs(s3): add troubleshooting to veeam tutorial MTA-4808b

* docs(s3): update

* docs(s3): update

* Update tutorials/veeam-backup-replication-s3/index.mdx

Co-authored-by: Jessica <[email protected]>

---------

Co-authored-by: Jessica <[email protected]>

Author: SamyOubouaziz

tutorials/veeam-backup-replication-s3/index.mdx

@@ -158,4 +158,82 @@ The following schema represents the functionality of Veeam Backup and Restore wh
 
 Veeam proceeds with the backup and stores data on Object Storage. To verify it, log yourself into the [Scaleway console](https://console.scaleway.com), enter the Object Storage section, and choose the Bucket used for Veeam. Several files and folders created by the application are visible:
 
-<Lightbox src="scaleway-veeam-backup-files.webp" alt="" />
+<Lightbox src="scaleway-veeam-backup-files.webp" alt="" />
+
+## Troubleshooting
+
+This section is designed to help you solve common issues encountered while performing the actions described in the procedure.
+
+### Bucket access errors
+
+#### Error messages
+
+- `Failed to preprocess target Error: S3 error: Access Denied`
+- `Error: Shared memory connection was closed.`
+- `Failed to upload disk 'shadowSpec>'`
+- `Agent failed to process method {DataTransfer.SyncDisk}.`
+
+#### Cause
+
+The application cannot access the S3 resource.
+
+#### Solution
+
+If you encounter one or several of the error messages above:
+
+- make sure that you have the `ObjectStorageFullAccess` [IAM permission](/identity-and-access-management/iam/concepts/#permission).
+
+- make sure that there is no [bucket policy](/storage/object/api-cli/bucket-policy/) preventing the application to access your bucket.
+
+### Too many requests error
+
+#### Error messages
+
+- `Error: S3 error: Too Many Requests`
+- `Code: Too Many Requests`
+- `Shared memory connection was closed.`
+- `Agent failed to process method {DataTransfer.SyncDisk}.`
+
+#### Cause
+
+Scaleway Object Storage applies a rate limit on PUT operations for safety reasons.
+
+#### Solution
+
+You can limit the number of concurrent tasks and update the timeout duration of S3 requests on the Veeam Backup & Replication server managing the backup copy operation by adding the elements below:
+
+```
+HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication
+
+S3ConcurrentTaskLimit
+Type: REG_DWORD
+Value: 8
+
+Type: DWORD
+Name: S3RequestTimeoutSec
+Value: 900
+
+Type: DWORD
+Name: S3RequestRetryTotalTimeoutSec
+Value: 9000
+```
+
+Then, restart every Veeam service, or restart the Veeam server.
+
+<Message type="note">
+You may experience reduced throughput due to the limitation.
+</Message>
+
+### Going further
+
+If you did not manage to identify the error and solve it by yourself, [open a support ticket](/console/account/how-to/open-a-support-ticket/), and provide as many details as possible, along with the necessary information below:
+
+- S3 Endpoint (e.g. `s3.fr-par.scw.cloud`)
+- Bucket name
+- Object name (if the request concerns an object)
+- Request type (PUT, GET, etc.)
+- HTTP status code
+- Date and time (timestamp)
+- User-agent (SDK, client, console, etc.)
+- Transaction ID (if possible)
+- Log / trace of the error (if possible)