Gateway–Virtual Tape Library (Gateway-VTL) Architecture
Gateway-VTL offers a durable, cost-effective solution to archive your data in the AWS cloud. The VTL interface it provides lets you leverage your existing tape-based backup application infrastructure to store data on virtual tape cartridges that you create on your gateway-VTL. Each gateway-VTL is preconfigured with a media changer and tape drives, which are available to your existing client backup applications as iSCSI devices. You add tape cartridges as you need to archive your data.
The following diagram provides an overview of the AWS Storage Gateway–VTL deployment.
The diagram identifies the following gateway-VTL components:
Virtual tape – Virtual tape is analogous to a physical tape cartridge. However, virtual tape data is stored in the AWS cloud. Like physical tapes, virtual tapes can be blank or can have data written on them. You can create virtual tapes either by using the AWS Storage Gateway console or programmatically by using the AWS Storage Gateway API. Each gateway can contain up to 1500 tapes or up to 1 PiB of total tape data at a time. The size of each virtual tape, which you can configure when you create the tape, is between 100 GiB and 2.5 TiB.
Virtual tape library (VTL) – A VTL is analogous to a physical tape library available on-premises with robotic arms and tape drives, including the collection of virtual tapes stored within the library. Each gateway-VTL comes with one VTL.
The virtual tapes that you create appear in your gateway's VTL. Tapes in the VTL are backed up by Amazon S3. As your backup software writes data to the gateway, the gateway stores data locally and then asynchronously uploads it to virtual tapes in your VTL—that is, Amazon Simple Storage Service (Amazon S3).
Tape drive – A VTL tape drive is analogous to a physical tape drive that can perform I/O and seek operations on a tape. Each VTL comes with a set of 10 tape drives, which are available to your backup application as iSCSI devices.
Media changer – A VTL media changer is analogous to a robot that moves tapes around in a physical tape library's storage slots and tape drives. Each VTL comes with one media changer, which is available to your backup application as an iSCSI device.
Virtual tape shelf (VTS) – A VTS is analogous to an off-site tape holding facility. You can archive tapes from your gateway's VTL to the VTS and, if needed, retrieve tapes from the VTS back to your gateway's VTL.
Archiving tapes – When your backup software ejects a tape, your gateway moves the tape to the VTS for long-term storage. The VTS is located in the AWS region in which you activated the gateway. Tapes in the VTS are stored in Amazon Glacier, an extremely low-cost storage service for data archiving and backup. For more information, go to Amazon Glacier.
Retrieving tapes – Tapes archived to the VTS cannot be read directly. To read an archived tape, you must first retrieve it to your gateway-VTL either by using the AWS Storage Gateway console or by using the AWS Storage Gateway API. A retrieved tape will be available in your VTL in about 24 hours.
You have one VTS in your account per AWS region. For example, if you create multiple gateways in the same AWS region, one VTS will hold ejected tapes for all the gateways. If you create gateways in different AWS regions, you will have one VTS per AWS region.
After you deploy and activate a gateway-VTL, you mount the virtual tape drives and media changer on your on-premises application servers as iSCSI devices. You create virtual tapes as needed and then use your existing backup software application to write data to the virtual tapes. The media changer loads and unloads the virtual tapes into the virtual tape drives for read and write operations.
Allocating Local Disks for the Gateway VM
Your gateway VM will need local disks, which you allocate for the following purposes:
Cache storage – The cache storage acts as the durable store for data that is waiting to upload to Amazon S3 from the upload buffer.
If your application reads data from a virtual tape, the gateway saves the data to the cache storage. The gateway stores recently accessed data in the cache storage for low-latency access. If your application requests tape data, the gateway first checks the cache storage for the data before downloading the data from AWS.
Upload buffer – The upload buffer provides a staging area for the gateway before it uploads the data to a virtual tape. The upload buffer is also critical for creating recovery points that you can use to recover tapes from unexpected failures. For more information, see You Need to Recover a Virtual Tape from a Malfunctioning Gateway-VTL.
As your backup application writes data to your gateway, the gateway copies data to both the cache storage and the upload buffer before acknowledging completion of the write operation to your backup application.
For guidelines to determine the amount of disk space you should allocate for the cache storage and upload buffer, see Deciding the Amount of Local Disk Storage.