create-cluster-replica.md 3.2 KB
title: "CREATE CLUSTER REPLICA"
description: "CREATE CLUSTER REPLICA provisions a new replica of a cluster."
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CREATE CLUSTER REPLICA provisions a new replica for an unmanaged
cluster.
{{< tip >}} When getting started with Materialize, we recommend starting with managed clusters. {{</ tip >}}
Conceptual framework
A cluster consists of zero or more replicas. Each replica of a cluster is a pool of compute resources that performs exactly the same computations on exactly the same data.
Using multiple replicas of a cluster facilitates fault tolerance. Clusters with multiple replicas can tolerate failures of the underlying hardware or network. As long as one replica remains reachable, the cluster as a whole remains available.
Syntax
{{< diagram "create-cluster-replica.svg" >}}
| Field | Use |
|---|---|
| _clustername | The cluster you want to attach a replica to. |
| _replicaname | A name for this replica. |
Options
{{% replica-options %}}
Details
Size
The SIZE option for replicas is identical to the SIZE option for
clusters option, except that the size applies only
to the new replica.
Credit usage
The replica will consume credits at a rate determined by its size:
| Size | Legacy size | Credits per hour |
|---|---|---|
25cc |
3xsmall |
0.25 |
50cc |
2xsmall |
0.5 |
100cc |
xsmall |
1 |
200cc |
small |
2 |
300cc |
3 | |
400cc |
medium |
4 |
600cc |
6 | |
800cc |
large |
8 |
1200cc |
12 | |
1600cc |
xlarge |
16 |
3200cc |
2xlarge |
32 |
6400cc |
3xlarge |
64 |
128C |
4xlarge |
128 |
256C |
5xlarge |
256 |
512C |
6xlarge |
512 |
Credit usage is measured at a one second granularity. Credit usage begins when a
CREATE CLUSTER REPLICA provisions the replica and ends when a DROP CLUSTER
REPLICA statement deprovisions the replica.
Homogeneous vs. heterogeneous hardware provisioning
Because Materialize uses active replication, all replicas will be instructed to do the same work, irrespective of their resource allocation.
For the most stable performance, we recommend using the same size and disk configuration for all replicas.
However, it is possible to use different replica configurations in the same cluster. In these cases, the replicas with less resources will likely be continually burdened with a backlog of work. If all of the faster replicas become unreachable, the system might experience delays in replying to requests while the slower replicas catch up to the last known time that the faster machines had computed.
Example
CREATE CLUSTER REPLICA c1.r1 (SIZE = '400cc');
Privileges
The privileges required to execute this statement are:
{{< include-md file="shared-content/sql-command-privileges/create-cluster-replica.md" >}}