5.5. Creating Distributed Volumes

This type of volume spreads files across the bricks in the volume.
Illustration of a distributed volume consisting of two servers. Two files are shown on the server1 brick, and one file is shown on the server2 brick. The distributed volume is set to a single mount point.

Figure 5.2. Illustration of a Distributed Volume

Warning

Distributed volumes can suffer significant data loss during a disk or server failure because directory contents are spread randomly across the bricks in the volume.
Use distributed volumes where scalable storage and redundancy is either not important, or is provided by other hardware or software layers.

Create a Distributed Volume

Use gluster volume create command to create different types of volumes, and gluster volume info command to verify successful volume creation.

Prerequisites

  1. Run the gluster volume create command to create the distributed volume.
    The syntax is gluster volume create NEW-VOLNAME [transport tcp | rdma | tcp,rdma] NEW-BRICK...
    The default value for transport is tcp. Other options can be passed such as auth.allow or auth.reject. See Section 11.1, “Configuring Volume Options” for a full list of parameters.
    Red Hat recommends disabling the performance.client-io-threads option on distributed volumes, as this option tends to worsen performance. Run the following command to disable performance.client-io-threads: 
    # gluster volume set VOLNAME performance.client-io-threads off

    Example 5.1. Distributed Volume with Two Storage Servers

    # gluster volume create test-volume server1:/rhgs/brick1 server2:/rhgs/brick1
Creation of test-volume has been successful
Please start the volume to access data.

    Example 5.2. Distributed Volume over InfiniBand with Four Servers

    # gluster volume create test-volume transport rdma server1:/rhgs/brick1 server2:/rhgs/brick1 server3:/rhgs/brick1 server4:/rhgs/brick1
Creation of test-volume has been successful
Please start the volume to access data.
  2. Run # gluster volume start VOLNAME to start the volume. 
    # gluster volume start test-volume
Starting test-volume has been successful
  3. Run gluster volume info command to optionally display the volume information.
    The following output is the result of Example 5.1, “Distributed Volume with Two Storage Servers”. 
    # gluster volume info
Volume Name: test-volume
Type: Distribute
Status: Created
Number of Bricks: 2
Transport-type: tcp
Bricks:
Brick1: server1:/rhgs/brick
Brick2: server2:/rhgs/brick