Connection errors

Replication and Disaster Recovery Administration Guide for Hitachi NAS Platform

Part Number

When attempting to add a new replication policy, a connection error may be indicated by “Unable to connect to <IP address>“ or “Error accessing <source/destination> server".

The “Unable to connect to“ message means one of the following:

  • The server is not currently powered up or is temporarily disconnected from the network. The server must be available and properly connected when creating a replication policy.
  • The NDMP service may be disabled. The replication uses the NDMP service which must be enabled when adding or running replications. Please use the NDMP configuration page (or the ndmp-status command) to enable and start the NDMP service.
  • The gigabit Ethernet port providing access to the EVS which hosts the file system is not accessible from the NAS Manager. This may be the case if the network is set up with private subnetworks as commonly used with VLANs. In this case, the server may have been configured so that NAS Manager access is through the management ports instead of the ports set using the ndmp-management-ports-set command.

The "Error accessing server" message may occur as a result of restricting NDMP access using the ndmp-option command. The allowip and blockip options can be set such that the NAS Manager is not allowed to access the NDMP services using the standard routes. If the NDMP connection restrictions are definitely required, change the configuration of the server to allow NAS Manager access by way of the management ports using the ndmp-management-ports-set command. The NAS Manager connections then bypass the allowip/blockip checks.

The NAS Manager replication and data migration features use the NDMP service on the NAS server. The NDMP service is usually accessed by way of the IP address of the EVS which hosts the file system, this access usually happens through a gigabit Ethernet port. In some cases, the IP address is within a private subnetwork and is not accessible from the NAS Manager. When this is the case, the ndmp-management-ports-set command can be used to request that the NAS Manager access goes through the management ports and is then relayed to the NDMP service.

The ndmp-management-ports-set command takes two parameters which are the TCP ports. One is used to accept the incoming connection on the management port and one to pass the requests to the NDMP code. These must be ports that are not in use by any other service. In particular, these ports must not be the standard NDMP service port. The port numbers 10001 and 10002 usually work and, being next to the standard NDMP port 10000, can be useful in identifying the port usage.

Having set up the NDMP management ports this way, all NAS Manager replication and data migration NDMP accesses will be routed by way of the management port. Note that the actual data transfer connections involved are between the NAS server EVSs and do not run over the management connections. In particular, a replication between two NAS servers passes the data over a TCP connection between EVS IP addresses through the gigabit Ethernet ports. Therefore, the two EVSs must have IP addresses that can communicate with each other.