Chapter 4. Adding Servers to the Trusted Storage Pool A storage pool is a network of storage servers. When the first server starts, the storage pool consists of that server alone. Adding additional storage servers to the storage pool is achieved using the probe command from a running, trusted storage server. Important Before adding servers to the trusted storage pool, you must ensure that the ports specified in Chapter 3, Considerations for Red Hat Gluster Storage are open. On Red Hat Enterprise Linux 7, enable the glusterFS firewall service in the active zones for runtime and permanent mode using the following commands: To get a list of active zones, run the following command: To allow the firewall service in the active zones, run the following commands: For more information about using firewalls, see section Using Firewalls in the Red Hat Enterprise Linux 7 Security Guide : https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Using_Firewalls.html . Note When any two gluster commands are executed concurrently on the same volume, the following error is displayed: Another transaction is in progress. This behavior in the Red Hat Gluster Storage prevents two or more commands from simultaneously modifying a volume configuration, potentially resulting in an inconsistent state. Such an implementation is common in environments with monitoring frameworks such as the Red Hat Gluster Storage Console, and Red Hat Enterprise Virtualization Manager. For example, in a four node Red Hat Gluster Storage Trusted Storage Pool, this message is observed when gluster volume status VOLNAME command is executed from two of the nodes simultaneously. 4.1. Adding Servers to the Trusted Storage Pool The gluster peer probe [server] command is used to add servers to the trusted server pool. Note Probing a node from lower version to a higher version of Red Hat Gluster Storage node is not supported. Adding Three Servers to a Trusted Storage Pool Create a trusted storage pool consisting of three storage servers, which comprise a volume. Prerequisites The glusterd service must be running on all storage servers requiring addition to the trusted storage pool. See Chapter 22, Starting and Stopping the glusterd service for service start and stop commands. Server1 , the trusted storage server, is started. The host names of the target servers must be resolvable by DNS. Run gluster peer probe [server] from Server 1 to add additional servers to the trusted storage pool. Note Self-probing Server1 will result in an error because it is part of the trusted storage pool by default. All the servers in the Trusted Storage Pool must have RDMA devices if either RDMA or RDMA,TCP volumes are created in the storage pool. The peer probe must be performed using IP/hostname assigned to the RDMA device. Verify the peer status from all servers using the following command: Important If the existing trusted storage pool has a geo-replication session, then after adding the new server to the trusted storage pool, perform the steps listed at Section 10.6, "Starting Geo-replication on a Newly Added Brick, Node, or Volume" . Note Verify that time is synchronized on all Gluster nodes by using the following command:

Commands:
firewall-cmd --get-active-zones
firewall-cmd --zone= zone_name --add-service=glusterfs firewall-cmd --zone= zone_name --add-service=glusterfs --permanent
gluster peer probe server2 Probe successful gluster peer probe server3 Probe successful gluster peer probe server4 Probe successful
gluster peer status Number of Peers: 3 Hostname: server2 Uuid: 5e987bda-16dd-43c2-835b-08b7d55e94e5 State: Peer in Cluster (Connected) Hostname: server3 Uuid: 1e0ca3aa-9ef7-4f66-8f15-cbc348f29ff7 State: Peer in Cluster (Connected) Hostname: server4 Uuid: 3e0caba-9df7-4f66-8e5d-cbc348f29ff7 State: Peer in Cluster (Connected)
for peer in `gluster peer status | grep Hostname | awk -F':' '{print USD2}' | awk '{print USD1}'`; do clockdiff USDpeer; done