[ aws . rds ]

restore-db-cluster-from-snapshot

Description

Creates a new DB cluster from a DB snapshot or DB cluster snapshot. This action only applies to Aurora DB clusters.

The target DB cluster is created from the source snapshot with a default configuration. If you don’t specify a security group, the new DB cluster is associated with the default security group.

Note

This action only restores the DB cluster, not the DB instances for that DB cluster. You must invoke the CreateDBInstance action to create DB instances for the restored DB cluster, specifying the identifier of the restored DB cluster in DBClusterIdentifier . You can create DB instances only after the RestoreDBClusterFromSnapshot action has completed and the DB cluster is available.

For more information on Amazon Aurora, see What Is Amazon Aurora? in the Amazon Aurora User Guide.

Note

This action only applies to Aurora DB clusters.

See also: AWS API Documentation

See ‘aws help’ for descriptions of global parameters.

Synopsis

  restore-db-cluster-from-snapshot
[--availability-zones <value>]
--db-cluster-identifier <value>
--snapshot-identifier <value>
--engine <value>
[--engine-version <value>]
[--port <value>]
[--db-subnet-group-name <value>]
[--database-name <value>]
[--option-group-name <value>]
[--vpc-security-group-ids <value>]
[--tags <value>]
[--kms-key-id <value>]
[--enable-iam-database-authentication | --no-enable-iam-database-authentication]
[--backtrack-window <value>]
[--enable-cloudwatch-logs-exports <value>]
[--engine-mode <value>]
[--scaling-configuration <value>]
[--db-cluster-parameter-group-name <value>]
[--deletion-protection | --no-deletion-protection]
[--copy-tags-to-snapshot | --no-copy-tags-to-snapshot]
[--domain <value>]
[--domain-iam-role-name <value>]
[--cli-input-json | --cli-input-yaml]
[--generate-cli-skeleton <value>]
[--cli-auto-prompt <value>]

Options

--availability-zones (list)

Provides the list of Availability Zones (AZs) where instances in the restored DB cluster can be created.

(string)

Syntax:

"string" "string" ...

--db-cluster-identifier (string)

The name of the DB cluster to create from the DB snapshot or DB cluster snapshot. This parameter isn’t case-sensitive.

Constraints:

• Must contain from 1 to 63 letters, numbers, or hyphens

• First character must be a letter

• Can’t end with a hyphen or contain two consecutive hyphens

Example: my-snapshot-id

--snapshot-identifier (string)

The identifier for the DB snapshot or DB cluster snapshot to restore from.

You can use either the name or the Amazon Resource Name (ARN) to specify a DB cluster snapshot. However, you can use only the ARN to specify a DB snapshot.

Constraints:

• Must match the identifier of an existing Snapshot.

--engine (string)

The database engine to use for the new DB cluster.

Default: The same as source

Constraint: Must be compatible with the engine of the source

--engine-version (string)

The version of the database engine to use for the new DB cluster.

To list all of the available engine versions for aurora (for MySQL 5.6-compatible Aurora), use the following command:

aws rds describe-db-engine-versions --engine aurora --query "DBEngineVersions[].EngineVersion"

To list all of the available engine versions for aurora-mysql (for MySQL 5.7-compatible Aurora), use the following command:

aws rds describe-db-engine-versions --engine aurora-mysql --query "DBEngineVersions[].EngineVersion"

To list all of the available engine versions for aurora-postgresql , use the following command:

aws rds describe-db-engine-versions --engine aurora-postgresql --query "DBEngineVersions[].EngineVersion"

Note

If you aren’t using the default engine version, then you must specify the engine version.

Aurora MySQL

Example: 5.6.10a , 5.6.mysql_aurora.1.19.2 , 5.7.12 , 5.7.mysql_aurora.2.04.5

Aurora PostgreSQL

Example: 9.6.3 , 10.7

--port (integer)

The port number on which the new DB cluster accepts connections.

Constraints: This value must be 1150-65535

Default: The same port as the original DB cluster.

--db-subnet-group-name (string)

The name of the DB subnet group to use for the new DB cluster.

Constraints: If supplied, must match the name of an existing DB subnet group.

Example: mySubnetgroup

--database-name (string)

The database name for the restored DB cluster.

--option-group-name (string)

The name of the option group to use for the restored DB cluster.

--vpc-security-group-ids (list)

A list of VPC security groups that the new DB cluster will belong to.

(string)

Syntax:

"string" "string" ...

--tags (list)

The tags to be assigned to the restored DB cluster.

(structure)

Metadata assigned to an Amazon RDS resource consisting of a key-value pair.

Key -> (string)

A key is the required name of the tag. The string value can be from 1 to 128 Unicode characters in length and can’t be prefixed with “aws:” or “rds:”. The string can only contain only the set of Unicode letters, digits, white-space, ‘_’, ‘.’, ‘/’, ‘=’, ‘+’, ‘-‘ (Java regex: “^([\p{L}\p{Z}\p{N}_.:/=+-]*)$”).

Value -> (string)

A value is the optional value of the tag. The string value can be from 1 to 256 Unicode characters in length and can’t be prefixed with “aws:” or “rds:”. The string can only contain only the set of Unicode letters, digits, white-space, ‘_’, ‘.’, ‘/’, ‘=’, ‘+’, ‘-‘ (Java regex: “^([\p{L}\p{Z}\p{N}_.:/=+-]*)$”).

Shorthand Syntax:

Key=string,Value=string ...

JSON Syntax:

[
  {
    "Key": "string",
    "Value": "string"
  }
  ...
]

--kms-key-id (string)

The AWS KMS key identifier to use when restoring an encrypted DB cluster from a DB snapshot or DB cluster snapshot.

The KMS key identifier is the Amazon Resource Name (ARN) for the KMS encryption key. If you are restoring a DB cluster with the same AWS account that owns the KMS encryption key used to encrypt the new DB cluster, then you can use the KMS key alias instead of the ARN for the KMS encryption key.

If you don’t specify a value for the KmsKeyId parameter, then the following occurs:

• If the DB snapshot or DB cluster snapshot in SnapshotIdentifier is encrypted, then the restored DB cluster is encrypted using the KMS key that was used to encrypt the DB snapshot or DB cluster snapshot.

• If the DB snapshot or DB cluster snapshot in SnapshotIdentifier isn’t encrypted, then the restored DB cluster isn’t encrypted.

--enable-iam-database-authentication | --no-enable-iam-database-authentication (boolean)

A value that indicates whether to enable mapping of AWS Identity and Access Management (IAM) accounts to database accounts. By default, mapping is disabled.

For more information, see IAM Database Authentication in the Amazon Aurora User Guide.

--backtrack-window (long)

The target backtrack window, in seconds. To disable backtracking, set this value to 0.

Note

Currently, Backtrack is only supported for Aurora MySQL DB clusters.

Default: 0

Constraints:

• If specified, this value must be set to a number from 0 to 259,200 (72 hours).

--enable-cloudwatch-logs-exports (list)

The list of logs that the restored DB cluster is to export to Amazon CloudWatch Logs. The values in the list depend on the DB engine being used. For more information, see Publishing Database Logs to Amazon CloudWatch Logs in the Amazon Aurora User Guide .

(string)

Syntax:

"string" "string" ...

--engine-mode (string)

The DB engine mode of the DB cluster, either provisioned , serverless , parallelquery , global , or multimaster .

--scaling-configuration (structure)

For DB clusters in serverless DB engine mode, the scaling properties of the DB cluster.

MinCapacity -> (integer)

The minimum capacity for an Aurora DB cluster in serverless DB engine mode.

For Aurora MySQL, valid capacity values are 1 , 2 , 4 , 8 , 16 , 32 , 64 , 128 , and 256 .

For Aurora PostgreSQL, valid capacity values are 2 , 4 , 8 , 16 , 32 , 64 , 192 , and 384 .

The minimum capacity must be less than or equal to the maximum capacity.

MaxCapacity -> (integer)

The maximum capacity for an Aurora DB cluster in serverless DB engine mode.

For Aurora MySQL, valid capacity values are 1 , 2 , 4 , 8 , 16 , 32 , 64 , 128 , and 256 .

For Aurora PostgreSQL, valid capacity values are 2 , 4 , 8 , 16 , 32 , 64 , 192 , and 384 .

The maximum capacity must be greater than or equal to the minimum capacity.

AutoPause -> (boolean)

A value that indicates whether to allow or disallow automatic pause for an Aurora DB cluster in serverless DB engine mode. A DB cluster can be paused only when it’s idle (it has no connections).

Note

If a DB cluster is paused for more than seven days, the DB cluster might be backed up with a snapshot. In this case, the DB cluster is restored when there is a request to connect to it.

SecondsUntilAutoPause -> (integer)

The time, in seconds, before an Aurora DB cluster in serverless mode is paused.

TimeoutAction -> (string)

The action to take when the timeout is reached, either ForceApplyCapacityChange or RollbackCapacityChange .

ForceApplyCapacityChange sets the capacity to the specified value as soon as possible.

RollbackCapacityChange , the default, ignores the capacity change if a scaling point isn’t found in the timeout period.

Warning

If you specify ForceApplyCapacityChange , connections that prevent Aurora Serverless from finding a scaling point might be dropped.

For more information, see Autoscaling for Aurora Serverless in the Amazon Aurora User Guide .

Shorthand Syntax:

MinCapacity=integer,MaxCapacity=integer,AutoPause=boolean,SecondsUntilAutoPause=integer,TimeoutAction=string

JSON Syntax:

{
  "MinCapacity": integer,
  "MaxCapacity": integer,
  "AutoPause": true|false,
  "SecondsUntilAutoPause": integer,
  "TimeoutAction": "string"
}

--db-cluster-parameter-group-name (string)

The name of the DB cluster parameter group to associate with this DB cluster. If this argument is omitted, the default DB cluster parameter group for the specified engine is used.

Constraints:

• If supplied, must match the name of an existing default DB cluster parameter group.

• Must be 1 to 255 letters, numbers, or hyphens.

• First character must be a letter.

• Can’t end with a hyphen or contain two consecutive hyphens.

--deletion-protection | --no-deletion-protection (boolean)

A value that indicates whether the DB cluster has deletion protection enabled. The database can’t be deleted when deletion protection is enabled. By default, deletion protection is disabled.

--copy-tags-to-snapshot | --no-copy-tags-to-snapshot (boolean)

A value that indicates whether to copy all tags from the restored DB cluster to snapshots of the restored DB cluster. The default is not to copy them.

--domain (string)

Specify the Active Directory directory ID to restore the DB cluster in. The domain must be created prior to this operation.

--domain-iam-role-name (string)

Specify the name of the IAM role to be used when making API calls to the Directory Service.

--cli-input-json | --cli-input-yaml (string) Reads arguments from the JSON string provided. The JSON string follows the format provided by --generate-cli-skeleton. If other arguments are provided on the command line, those values will override the JSON-provided values. It is not possible to pass arbitrary binary values using a JSON-provided value as the string will be taken literally. This may not be specified along with --cli-input-yaml.

--generate-cli-skeleton (string) Prints a JSON skeleton to standard output without sending an API request. If provided with no value or the value input, prints a sample input JSON that can be used as an argument for --cli-input-json. Similarly, if provided yaml-input it will print a sample input YAML that can be used with --cli-input-yaml. If provided with the value output, it validates the command inputs and returns a sample output JSON for that command.

--cli-auto-prompt (boolean) Automatically prompt for CLI input parameters.

See ‘aws help’ for descriptions of global parameters.

Examples

To restore a DB cluster from a snapshot

The following restore-db-cluster-from-snapshot restores an Aurora PostgreSQL DB cluster compatible with PostgreSQL version 10.7 from a DB cluster snapshot named test-instance-snapshot.

aws rds restore-db-cluster-from-snapshot \
    --db-cluster-identifier newdbcluster \
    --snapshot-identifier test-instance-snapshot \
    --engine aurora-postgresql \
    --engine-version 10.7

Output:

{
    "DBCluster": {
        "AllocatedStorage": 1,
        "AvailabilityZones": [
            "us-west-2c",
            "us-west-2a",
            "us-west-2b"
        ],
        "BackupRetentionPeriod": 7,
        "DatabaseName": "",
        "DBClusterIdentifier": "newdbcluster",
        "DBClusterParameterGroup": "default.aurora-postgresql10",
        "DBSubnetGroup": "default",
        "Status": "creating",
        "Endpoint": "newdbcluster.cluster-############.us-west-2.rds.amazonaws.com",
        "ReaderEndpoint": "newdbcluster.cluster-ro-############.us-west-2.rds.amazonaws.com",
        "MultiAZ": false,
        "Engine": "aurora-postgresql",
        "EngineVersion": "10.7",
        "Port": 5432,
        "MasterUsername": "postgres",
        "PreferredBackupWindow": "09:33-10:03",
        "PreferredMaintenanceWindow": "sun:12:22-sun:12:52",
        "ReadReplicaIdentifiers": [],
        "DBClusterMembers": [],
        "VpcSecurityGroups": [
            {
                "VpcSecurityGroupId": "sg-########",
                "Status": "active"
            }
        ],
        "HostedZoneId": "Z1PVIF0EXAMPLE",
        "StorageEncrypted": true,
        "KmsKeyId": "arn:aws:kms:us-west-2:123456789012:key/287364e4-33e3-4755-a3b0-a1b2c3d4e5f6",
        "DbClusterResourceId": "cluster-5DSB5IFQDDUVAWOUWM1EXAMPLE",
        "DBClusterArn": "arn:aws:rds:us-west-2:123456789012:cluster:newdbcluster",
        "AssociatedRoles": [],
        "IAMDatabaseAuthenticationEnabled": false,
        "ClusterCreateTime": "2020-06-05T15:06:58.634Z",
        "EngineMode": "provisioned",
        "DeletionProtection": false,
        "HttpEndpointEnabled": false,
        "CopyTagsToSnapshot": false,
        "CrossAccountClone": false,
        "DomainMemberships": []
    }
}

For more information, see Restoring from a DB Cluster Snapshot in the Amazon Aurora User Guide.

Output

DBCluster -> (structure)

Contains the details of an Amazon Aurora DB cluster.

This data type is used as a response element in the DescribeDBClusters , StopDBCluster , and StartDBCluster actions.

AllocatedStorage -> (integer)

For all database engines except Amazon Aurora, AllocatedStorage specifies the allocated storage size in gibibytes (GiB). For Aurora, AllocatedStorage always returns 1, because Aurora DB cluster storage size isn’t fixed, but instead automatically adjusts as needed.

AvailabilityZones -> (list)

Provides the list of Availability Zones (AZs) where instances in the DB cluster can be created.

(string)

BackupRetentionPeriod -> (integer)

Specifies the number of days for which automatic DB snapshots are retained.

CharacterSetName -> (string)

If present, specifies the name of the character set that this cluster is associated with.

DatabaseName -> (string)

Contains the name of the initial database of this DB cluster that was provided at create time, if one was specified when the DB cluster was created. This same name is returned for the life of the DB cluster.

DBClusterIdentifier -> (string)

Contains a user-supplied DB cluster identifier. This identifier is the unique key that identifies a DB cluster.

DBClusterParameterGroup -> (string)

Specifies the name of the DB cluster parameter group for the DB cluster.

DBSubnetGroup -> (string)

Specifies information on the subnet group associated with the DB cluster, including the name, description, and subnets in the subnet group.

Status -> (string)

Specifies the current state of this DB cluster.

PercentProgress -> (string)

Specifies the progress of the operation as a percentage.

EarliestRestorableTime -> (timestamp)

The earliest time to which a database can be restored with point-in-time restore.

Endpoint -> (string)

Specifies the connection endpoint for the primary instance of the DB cluster.

ReaderEndpoint -> (string)

The reader endpoint for the DB cluster. The reader endpoint for a DB cluster load-balances connections across the Aurora Replicas that are available in a DB cluster. As clients request new connections to the reader endpoint, Aurora distributes the connection requests among the Aurora Replicas in the DB cluster. This functionality can help balance your read workload across multiple Aurora Replicas in your DB cluster.

If a failover occurs, and the Aurora Replica that you are connected to is promoted to be the primary instance, your connection is dropped. To continue sending your read workload to other Aurora Replicas in the cluster, you can then reconnect to the reader endpoint.

CustomEndpoints -> (list)

Identifies all custom endpoints associated with the cluster.

(string)

MultiAZ -> (boolean)

Specifies whether the DB cluster has instances in multiple Availability Zones.

Engine -> (string)

Provides the name of the database engine to be used for this DB cluster.

EngineVersion -> (string)

Indicates the database engine version.

LatestRestorableTime -> (timestamp)

Specifies the latest time to which a database can be restored with point-in-time restore.

Port -> (integer)

Specifies the port that the database engine is listening on.

MasterUsername -> (string)

Contains the master username for the DB cluster.

DBClusterOptionGroupMemberships -> (list)

Provides the list of option group memberships for this DB cluster.

(structure)

Contains status information for a DB cluster option group.

DBClusterOptionGroupName -> (string)

Specifies the name of the DB cluster option group.

Status -> (string)

Specifies the status of the DB cluster option group.

PreferredBackupWindow -> (string)

Specifies the daily time range during which automated backups are created if automated backups are enabled, as determined by the BackupRetentionPeriod .

PreferredMaintenanceWindow -> (string)

Specifies the weekly time range during which system maintenance can occur, in Universal Coordinated Time (UTC).

ReplicationSourceIdentifier -> (string)

Contains the identifier of the source DB cluster if this DB cluster is a read replica.

ReadReplicaIdentifiers -> (list)

Contains one or more identifiers of the read replicas associated with this DB cluster.

(string)

DBClusterMembers -> (list)

Provides the list of instances that make up the DB cluster.

(structure)

Contains information about an instance that is part of a DB cluster.

DBInstanceIdentifier -> (string)

Specifies the instance identifier for this member of the DB cluster.

IsClusterWriter -> (boolean)

Value that is true if the cluster member is the primary instance for the DB cluster and false otherwise.

DBClusterParameterGroupStatus -> (string)

Specifies the status of the DB cluster parameter group for this member of the DB cluster.

PromotionTier -> (integer)

A value that specifies the order in which an Aurora Replica is promoted to the primary instance after a failure of the existing primary instance. For more information, see Fault Tolerance for an Aurora DB Cluster in the Amazon Aurora User Guide .

VpcSecurityGroups -> (list)

Provides a list of VPC security groups that the DB cluster belongs to.

(structure)

This data type is used as a response element for queries on VPC security group membership.

VpcSecurityGroupId -> (string)

The name of the VPC security group.

Status -> (string)

The status of the VPC security group.

HostedZoneId -> (string)

Specifies the ID that Amazon Route 53 assigns when you create a hosted zone.

StorageEncrypted -> (boolean)

Specifies whether the DB cluster is encrypted.

KmsKeyId -> (string)

If StorageEncrypted is enabled, the AWS KMS key identifier for the encrypted DB cluster.

DbClusterResourceId -> (string)

The AWS Region-unique, immutable identifier for the DB cluster. This identifier is found in AWS CloudTrail log entries whenever the AWS KMS key for the DB cluster is accessed.

DBClusterArn -> (string)

The Amazon Resource Name (ARN) for the DB cluster.

AssociatedRoles -> (list)

Provides a list of the AWS Identity and Access Management (IAM) roles that are associated with the DB cluster. IAM roles that are associated with a DB cluster grant permission for the DB cluster to access other AWS services on your behalf.

(structure)

Describes an AWS Identity and Access Management (IAM) role that is associated with a DB cluster.

RoleArn -> (string)

The Amazon Resource Name (ARN) of the IAM role that is associated with the DB cluster.

Status -> (string)

Describes the state of association between the IAM role and the DB cluster. The Status property returns one of the following values:

• ACTIVE - the IAM role ARN is associated with the DB cluster and can be used to access other AWS services on your behalf.

• PENDING - the IAM role ARN is being associated with the DB cluster.

• INVALID - the IAM role ARN is associated with the DB cluster, but the DB cluster is unable to assume the IAM role in order to access other AWS services on your behalf.

FeatureName -> (string)

The name of the feature associated with the AWS Identity and Access Management (IAM) role. For the list of supported feature names, see DBEngineVersion .

IAMDatabaseAuthenticationEnabled -> (boolean)

A value that indicates whether the mapping of AWS Identity and Access Management (IAM) accounts to database accounts is enabled.

CloneGroupId -> (string)

Identifies the clone group to which the DB cluster is associated.

ClusterCreateTime -> (timestamp)

Specifies the time when the DB cluster was created, in Universal Coordinated Time (UTC).

EarliestBacktrackTime -> (timestamp)

The earliest time to which a DB cluster can be backtracked.

BacktrackWindow -> (long)

The target backtrack window, in seconds. If this value is set to 0, backtracking is disabled for the DB cluster. Otherwise, backtracking is enabled.

BacktrackConsumedChangeRecords -> (long)

The number of change records stored for Backtrack.

EnabledCloudwatchLogsExports -> (list)

A list of log types that this DB cluster is configured to export to CloudWatch Logs.

Log types vary by DB engine. For information about the log types for each DB engine, see Amazon RDS Database Log Files in the Amazon Aurora User Guide.

(string)

Capacity -> (integer)

The current capacity of an Aurora Serverless DB cluster. The capacity is 0 (zero) when the cluster is paused.

For more information about Aurora Serverless, see Using Amazon Aurora Serverless in the Amazon Aurora User Guide .

EngineMode -> (string)

The DB engine mode of the DB cluster, either provisioned , serverless , parallelquery , global , or multimaster .

Note

global engine mode only applies for global database clusters created with Aurora MySQL version 5.6.10a. For higher Aurora MySQL versions, the clusters in a global database use provisioned engine mode. To check if a DB cluster is part of a global database, use DescribeGlobalClusters instead of checking the EngineMode return value from DescribeDBClusters .

ScalingConfigurationInfo -> (structure)

Shows the scaling configuration for an Aurora DB cluster in serverless DB engine mode.

For more information, see Using Amazon Aurora Serverless in the Amazon Aurora User Guide .

MinCapacity -> (integer)

The maximum capacity for the Aurora DB cluster in serverless DB engine mode.

MaxCapacity -> (integer)

The maximum capacity for an Aurora DB cluster in serverless DB engine mode.

AutoPause -> (boolean)

A value that indicates whether automatic pause is allowed for the Aurora DB cluster in serverless DB engine mode.

When the value is set to false for an Aurora Serverless DB cluster, the DB cluster automatically resumes.

SecondsUntilAutoPause -> (integer)

The remaining amount of time, in seconds, before the Aurora DB cluster in serverless mode is paused. A DB cluster can be paused only when it’s idle (it has no connections).

TimeoutAction -> (string)

The timeout action of a call to ModifyCurrentDBClusterCapacity , either ForceApplyCapacityChange or RollbackCapacityChange .

DeletionProtection -> (boolean)

Indicates if the DB cluster has deletion protection enabled. The database can’t be deleted when deletion protection is enabled.

HttpEndpointEnabled -> (boolean)

A value that indicates whether the HTTP endpoint for an Aurora Serverless DB cluster is enabled.

When enabled, the HTTP endpoint provides a connectionless web service API for running SQL queries on the Aurora Serverless DB cluster. You can also query your database from inside the RDS console with the query editor.

For more information, see Using the Data API for Aurora Serverless in the Amazon Aurora User Guide .

ActivityStreamMode -> (string)

The mode of the database activity stream. Database events such as a change or access generate an activity stream event. The database session can handle these events either synchronously or asynchronously.

ActivityStreamStatus -> (string)

The status of the database activity stream.

ActivityStreamKmsKeyId -> (string)

The AWS KMS key identifier used for encrypting messages in the database activity stream.

ActivityStreamKinesisStreamName -> (string)

The name of the Amazon Kinesis data stream used for the database activity stream.

CopyTagsToSnapshot -> (boolean)

Specifies whether tags are copied from the DB cluster to snapshots of the DB cluster.

CrossAccountClone -> (boolean)

Specifies whether the DB cluster is a clone of a DB cluster owned by a different AWS account.

DomainMemberships -> (list)

The Active Directory Domain membership records associated with the DB cluster.

(structure)

An Active Directory Domain membership record associated with the DB instance or cluster.

Domain -> (string)

The identifier of the Active Directory Domain.

Status -> (string)

The status of the Active Directory Domain membership for the DB instance or cluster. Values include joined, pending-join, failed, and so on.

FQDN -> (string)

The fully qualified domain name of the Active Directory Domain.

IAMRoleName -> (string)

The name of the IAM role to be used when making API calls to the Directory Service.

GlobalWriteForwardingStatus -> (string)

Specifies whether a secondary cluster in an Aurora global database has write forwarding enabled, not enabled, or is in the process of enabling it.

GlobalWriteForwardingRequested -> (boolean)

Specifies whether you have requested to enable write forwarding for a secondary cluster in an Aurora global database. Because write forwarding takes time to enable, check the value of GlobalWriteForwardingStatus to confirm that the request has completed before using the write forwarding feature for this cluster.