Using Pre-Conditions

Data Migrator Administration Guide for Hitachi NAS Platform

Part Number

When a migration policy is scheduled to run, it evaluates the percentage of available free space in the Policy's primary storage. Based on this analysis, one rule may be triggered to define the data set subject to migration. Migrations of data from primary storage then occurs based on the statements in the rule that was triggered. Only a single rule will be engaged during any particular migration operation.

When defining pre-conditions, customer support recommends aggressive tiering; specifically, it may be desirable to migrate .mp3 files and the contents of the directory /tmp regardless of the available free space. Then, if free space on primary storage is reduced to less than 50%, also to migrate all files not accessed within the last sixty days. Finally, if available free space is reduced to less than 15%, also to migrate the contents of users' home directories.

The following rules illustrate this scenario:
Rule Statement
Rule 1: INCLUDE (<FILENAME *.mp3>) OR <PATH /tmp/*)
Rule 2: INCLUDE (<FILENAME *.mp3>) OR <PATH /tmp/*)
Rule 3: INCLUDE (<FILENAME *.mp3>) OR <PATH /tmp/*)
INCLUDE (<PATH /home/*>)

Related pre-conditions

  • Rule 3 if free space is less than 15%.
  • Rule 2 if free space is less than 50%.
  • Rule 1 if no other condition applies.

When the migration policy is scheduled to run, different rules may be triggered based on the available free space on primary storage. When a migration policy is engaged, only a single rule will be triggered to run.

For example:
  • If free space is at 80%, then Rule 1 will be used.
  • If free space is at 40%, then Rule 2 will be used.
  • If free space is at 10%, then Rule 3 will be used.

When percentage thresholds are specified, they are evaluated based on whole number percentages. This means that if two rules are specified, one that will take effect at 8% of free space and one at 9% of free space, if the file system has 8.5% free space available, then the rule with the 8% pre-condition will apply.

Note: If the primary storage defined in the migration path is a virtual volume, free space will be based on the limit defined by the virtual volume quota. If this quota has not been defined, then free space available will be based on the free space of the file system hosting the virtual volume.

Connection Errors

When attempting to add a new migration policy, a connection error may be indicated by a message saying "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 migration policy.
  • The NDMP service may be disabled. The migration uses the NDMP service which must be enabled when adding or running replications. 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 SMU. 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 SMU 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 SMU is not allowed to access the NDMP services via the standard routes. If the NDMP connection restrictions are definitely required, change the configuration of the server to allow SMU access via the management ports using the ndmp-management-ports-set command. The SMU connections then bypass the allowip/blockip checks.