Storage Gateway VTL developer manual?

With Tape Gateway, the customer does not need to worry about setting SCSI timeouts for retrieving tapes from Glacier. Tapes go from S3 to S3 Glacier or S3 Glacier Deep Archive when the customer ejects/exports the tape from backup application.

Retrieving a tape is a 2-step process. A customer needs to use SGW API or console to retrieve the file from Glacier or Deep Archive to gateway's virtual tape library first (which is S3). Once the tape is in S3, they can present the tape through the gateway to the backup application.

I have included a link below that goes through the retrieval process. The relevant section is "Retrieving Archived Tapes".

https://docs.aws.amazon.com/storagegateway/latest/userguide/managing-gateway-vtl.html#retrieving-archived-tapes-vtl

Hope this helps. Please let me know if there are any other questions.