8.4. Creating Replicated Volumes

Important

Creating replicated volume with rep_count > 2 is under technology preview. Technology Preview features are not fully supported under Red Hat subscription level agreements (SLAs), may not be functionally complete, and are not intended for production use. However, these features provide early access to upcoming product innovations, enabling customers to test functionality and provide feedback during the development process. As Red Hat considers making future iterations of Technology Preview features generally available, we will provide commercially reasonable efforts to resolve any reported issues that customers experience when using these features.
Replicated volumes create copies of files across multiple bricks in the volume. You can use replicated volumes in environments where high-availability and high-reliability are critical.

Note

The number of bricks should be equal to the replica count for a replicated volume. To protect against server and disk failures, it is recommended that the bricks of the volume are from different servers.
Illustration of a Replicated Volume

Figure 8.2. Illustration of a Replicated Volume


To create a replicated volume
  1. Create a trusted storage pool as described earlier in Section 7.1, “Adding Servers to Trusted Storage Pool”.
  2. Create the replicated volume:
    # gluster volume create NEW-VOLNAME [replica COUNT] [transport tcp | rdma | tcp,rdma] NEW-BRICK...
    For example, to create a replicated volume with two storage servers:
    # gluster volume create test-volume replica 2 transport tcp server1:/exp1 server2:/exp2
    Creation of test-volume has been successful
    Please start the volume to access data.
    The order in which the bricks are specified determines the mirroring of bricks with each other. For example, first n bricks, where n is the replica count. Hence, the first two bricks specified will mirror each other, and the third and fourth bricks will mirror each other.
    If the transport type is not specified, tcp is used as the default. You can also set additional options if required, such as auth.allow or auth.reject. For more information, see Section 10.1, “Tuning Volume Options”

    Note

    Make sure you start your volumes before you try to mount them or else client operations after the mount will hang, see Section 8.10, “Starting Volumes ” for details.