Write snapshots with EBS direct APIs - Amazon EBS
Start a snapshotPut data into a snapshotComplete a snapshot
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Write snapshots with EBS direct APIs

The following steps describe how to use the EBS direct APIs to write incremental snapshots:

  1. Use the StartSnapshot action and specify a parent snapshot ID to start a snapshot as an incremental snapshot of an existing one, or omit the parent snapshot ID to start a new snapshot. This action returns the new snapshot ID, which is in a pending state.

  2. Use the PutSnapshotBlock action and specify the ID of the pending snapshot to add data to it in the form of individual blocks. You must specify a Base64-encoded SHA256 checksum for the block of data transmitted. The service computes the checksum of the data received and validates it with the checksum that you specified. The action fails if the checksums don't match.

  3. When you're done adding data to the pending snapshot, use the CompleteSnapshot action to start an asynchronous workflow that seals the snapshot and moves it to a completed state.

Repeat these steps to create a new, incremental snapshot using the previously created snapshot as the parent.

For example, in the following diagram, snapshot A is the first new snapshot started. Snapshot A is used as the parent snapshot to start snapshot B. Snapshot B is used as the parent snapshot to start and create snapshot C. Snapshots A, B, and C are incremental snapshots. Snapshot A is used to create EBS volume 1. Snapshot D is created from EBS volume 1. Snapshot D is an incremental snapshot of A; it is not an incremental snapshot of B or C.

EBS direct APIs used to create incremental snapshots.

The following examples show how to write snapshots using the EBS direct APIs.

Start a snapshot

Amazon CLI

The following start-snapshot example command starts an 8 GiB snapshot, using snapshot snap-123EXAMPLE1234567 as the parent snapshot. The new snapshot will be an incremental snapshot of the parent snapshot. The snapshot moves to an error state if there are no put or complete requests made for the snapshot within the specified 60 minute timeout period. The 550e8400-e29b-41d4-a716-446655440000 client token ensures idempotency for the request. If the client token is omitted, the Amazon SDK automatically generates one for you. For more information about idempotency, see Idempotency for StartSnapshot API.

aws ebs start-snapshot --volume-size 8 --parent-snapshot snap-123EXAMPLE1234567 --timeout 60 --client-token 550e8400-e29b-41d4-a716-446655440000

The following example response for the previous command shows the snapshot ID, Amazon account ID, status, volume size in GiB, and size of the blocks in the snapshot. The snapshot is started in a pending state. Specify the snapshot ID in subsequent put-snapshot-block commands to write data to the snapshot, then use the complete-snapshot command to complete the snapshot and change its status to completed.

{
    "SnapshotId": "snap-0aaEXAMPLEe306d62",
    "OwnerId": "111122223333",
    "Status": "pending",
    "VolumeSize": 8,
    "BlockSize": 524288
}
Amazon API

The following StartSnapshot example request starts an 8 GiB snapshot, using snapshot snap-123EXAMPLE1234567 as the parent snapshot. The new snapshot will be an incremental snapshot of the parent snapshot. The snapshot moves to an error state if there are no put or complete requests made for the snapshot within the specified 60 minute timeout period. The 550e8400-e29b-41d4-a716-446655440000 client token ensures idempotency for the request. If the client token is omitted, the Amazon SDK automatically generates one for you. For more information about idempotency, see Idempotency for StartSnapshot API.

POST /snapshots HTTP/1.1
Host: ebs.us-east-2.amazonaws.com
Accept-Encoding: identity
User-Agent: <User agent parameter>
X-Amz-Date: 20200618T040724Z
Authorization: <Authentication parameter>

{
    "VolumeSize": 8,
    "ParentSnapshot": snap-123EXAMPLE1234567,
    "ClientToken": "550e8400-e29b-41d4-a716-446655440000",
    "Timeout": 60
}

The following example response for the previous request shows the snapshot ID, Amazon account ID, status, volume size in GiB, and size of the blocks in the snapshot. The snapshot is started in a pending state. Specify the snapshot ID in a subsequent PutSnapshotBlocks request to write data to the snapshot.

HTTP/1.1 201 Created
x-amzn-RequestId: 929e6eb9-7183-405a-9502-5b7da37c1b18
Content-Type: application/json
Content-Length: 181
Date: Thu, 18 Jun 2020 04:07:29 GMT
Connection: keep-alive

{
    "BlockSize": 524288,
    "Description": null,
    "OwnerId": "138695307491",
    "Progress": null,
    "SnapshotId": "snap-052EXAMPLEc85d8dd",
    "StartTime": null,
    "Status": "pending",
    "Tags": null,
    "VolumeSize": 8
}

Put data into a snapshot

Amazon CLI

The following put-snapshot example command writes 524288 Bytes of data to block index 1000 on snapshot snap-0aaEXAMPLEe306d62. The Base64 encoded QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM= checksum was generated using the SHA256 algorithm. The data that is transmitted is in the /tmp/data file.

aws ebs put-snapshot-block --snapshot-id snap-0aaEXAMPLEe306d62 --block-index 1000 --data-length 524288 --block-data /tmp/data --checksum QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM= --checksum-algorithm SHA256

The following example response for the previous command confirms the data length, checksum, and checksum algorithm for the data received by the service.

{
    "DataLength": "524288",
    "Checksum": "QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM=",
    "ChecksumAlgorithm": "SHA256"
}
Amazon API

The following PutSnapshot example request writes 524288 Bytes of data to block index 1000 on snapshot snap-052EXAMPLEc85d8dd. The Base64 encoded QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM= checksum was generated using the SHA256 algorithm. The data is transmitted in the body of the request and is represented as BlockData in the following example.

PUT /snapshots/snap-052EXAMPLEc85d8dd/blocks/1000 HTTP/1.1
Host: ebs.us-east-2.amazonaws.com
Accept-Encoding: identity
x-amz-Data-Length: 524288
x-amz-Checksum: QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM=
x-amz-Checksum-Algorithm: SHA256
User-Agent: <User agent parameter>
X-Amz-Date: 20200618T042215Z
X-Amz-Content-SHA256: UNSIGNED-PAYLOAD
Authorization: <Authentication parameter>
          
          BlockData

The following is example response for the previous request confirms the data length, checksum, and checksum algorithm for the data received by the service. 

HTTP/1.1 201 Created
x-amzn-RequestId: 643ac797-7e0c-4ad0-8417-97b77b43c57b
x-amz-Checksum: QOD3gmEQOXATfJx2Aa34W4FU2nZGyXfqtsUuktOw8DM=
x-amz-Checksum-Algorithm: SHA256
Content-Type: application/json
Content-Length: 2
Date: Thu, 18 Jun 2020 04:22:12 GMT
Connection: keep-alive

{}

Complete a snapshot

Amazon CLI

The following complete-snapshot example command completes snapshot snap-0aaEXAMPLEe306d62. The command specifies that 5 blocks were written to the snapshot. The 6D3nmwi5f2F0wlh7xX8QprrJBFzDX8aacdOcA3KCM3c= checksum represents the checksum for the complete set of data written to a snapshot. For more information about checksums, see Use checksums earlier in this guide.

aws ebs complete-snapshot --snapshot-id snap-0aaEXAMPLEe306d62 --changed-blocks-count 5 --checksum 6D3nmwi5f2F0wlh7xX8QprrJBFzDX8aacdOcA3KCM3c= --checksum-algorithm SHA256 --checksum-aggregation-method LINEAR

The following is an example response for the previous command.

{
    "Status": "pending"
}
Amazon API

The following CompleteSnapshot example request completes snapshot snap-052EXAMPLEc85d8dd. The command specifies that 5 blocks were written to the snapshot. The 6D3nmwi5f2F0wlh7xX8QprrJBFzDX8aacdOcA3KCM3c= checksum represents the checksum for the complete set of data written to a snapshot.

POST /snapshots/completion/snap-052EXAMPLEc85d8dd HTTP/1.1
Host: ebs.us-east-2.amazonaws.com
Accept-Encoding: identity
x-amz-ChangedBlocksCount: 5
x-amz-Checksum: 6D3nmwi5f2F0wlh7xX8QprrJBFzDX8aacdOcA3KCM3c=
x-amz-Checksum-Algorithm: SHA256
x-amz-Checksum-Aggregation-Method: LINEAR
User-Agent: <User agent parameter>
X-Amz-Date: 20200618T043158Z
Authorization: <Authentication parameter>

The following is an example response for the previous request.

HTTP/1.1 202 Accepted
x-amzn-RequestId: 06cba5b5-b731-49de-af40-80333ac3a117
Content-Type: application/json
Content-Length: 20
Date: Thu, 18 Jun 2020 04:31:50 GMT
Connection: keep-alive

{"Status":"pending"}