Configuring NDMP backup prefetch

The NDMP backup prefetch function navigates the directory that is being backed up, reading files in advance of the files actually coming due to be backed up. The prefetch function opens files in read-only mode and places the files in the cache of the file module for improved backup performance. Use the cfgndmpprefetch CLI command to configure, activate and deactivate the NDMP backup prefetch function. You can also use the graphical user interface (GUI) to work with this function.

Restriction: NDMP backup prefetch is designed to work on files that are less than or equal to 1MB in size. NDMP backup prefetch will not work for a file system that has block size that is greater than 1MB.

To activate the NDMP backup prefetch feature, use the cfgndmpprefetch CLI command with the --activate option, specifying the NDMP file module group, as in the following example:

cfgndmpprefetch ndmpg1 --activate

If NDMP is not active on the specified NDMP file module group, a message is displayed indicating that prefetch for NDMP will be activated when NDMP is activated.

When you attempt to change the NDMP prefetch configuration while the NDMP node group is active (similarly to when you attempt to change an NDMP configuration option while the NDMP node group is active), the system displays the following message:

EFSSG0448W Command requires NDMP to be deactivated before configuration can change. 
Deactivating NDMP will stop all NDMP sessions currently in progress and not allow 
new NDMP sessions to start for this NDMP node group. Depending on how many NDMP 
sessions will be killed (if any), there may be some delay.
Do you really want to perform the operation (yes/no - default no):

If you enter yes, the NDMP configuration is deactivated, the configuration is changed, and the configuration is reactivated. Any NDMP operations, such as backups and restores, which were in progress on the specified NDMP file module group, stop prematurely, and are not automatically restarted when the cfgndmp command completes. To complete an interrupted operation, it must be restarted manually.

To deactivate the NDMP backup prefetch feature, use the cfgndmpprefetch CLI command with the --deactivate option, specifying the NDMP file module group, as in the following example:

cfgndmpprefetch ndmpg1 --deactivate

If NDMP is not active on the specified NDMP file module, a message is displayed indicating that prefetch for NDMP will be deactivated when NDMP is activated.

To set a limit for the number of applications that can simultaneously use NDMP backup prefetch for a file module, including multiple instances of the same program such as multiple NDMP sessions, use the cfgndmpprefetch CLI command with the --applimit option, as in the following example:

cfgndmpprefetch ndmpg1 --appLimit 4

If NDMP is not active on the specified NDMP file module group, a message is displayed indicating that the configuration for Prefetch for NDMP has been updated.

The value for the --applimit option must be a positive integer greater than 0 and less than or equal to 10. The default value is 4.

To set a limit for the number of prefetching threads per file module, use the cfgndmpprefetch CLI command with the --numThreads option, as in the following example:

cfgndmpprefetch ndmpg1 --numThreads 100

If NDMP is not active on the specified NDMP file module group, a message is displayed indicating that the configuration for Prefetch for NDMP has been updated.

The value for the --numThreads option must be a positive integer greater than 50 and less than or equal to 180. The default value is 100.

To display NDMP backup prefetch status information, use the lsndmpprefetch CLI command using the -s or --status option, and optionally adding the -g option to limit display to the specified NDMP file module group, as in the following example:

lsndmpprefetch -s

Output is displayed in the following format:

NODES_GROUP_NAME NODE                       NDMP_SERVICE_STATUS
NDMPTEST         mgmt002st001(192.168.132.2) RUNNING
NDMPTEST         mgmt001st001(192.168.132.1) RUNNING

If the -g option is not specified, status information for both file module group file modules is displayed by default.

To display NDMP backup prefetch default configuration information, use the lsndmpprefetch CLI command using the -d or --default option, as in the following example:

lsndmpprefetch -d

Output is displayed in the following format:

NODES_GROUP_NAME NETWORK_GROUP_ATTACHED AUTHORIZED_NDMP_CLIENTS NDMP_PORT DATA_TRANSFER_PORT_RANGE NDMP_TCP_WINDOW_SIZE DATA_IP DEFAULT_PROTOCOL_VERSION FILE_SYSTEM_PATHS LOG_FILE_TRACE_LEVEL NDMP_USRENAME ENABLE_NEW_SESSIONS
DEFAULT                                                         10000     2048-2098                160                          4                                          0                    ndmp          allow

You cannot specify a file module group using the -g option or use the -s or --status options when using the -d or --default default options.

To display lsndmpprefetch command output as colon-delimited fields, use the -Y option.

All prefetch code running on all of the file modules on a file module group is at the same code level with the same configuration, so if an NDMP session with prefetch activated begins on one file module and fails because the file module fails, the session can begin again on another file module. Restarting the NDMP session on another file module is a manual process unless the timeout configured for the DMA allows the session to be restarted after the IP address has automatically been moved to another file module.

A default NDMP backup prefetch configuration is assigned to a newly created NDMP file module group, with the function deactivated. Messages generated by the function are posted to the alert log.

GUI navigation

To work with this function in the management GUI, log on to the GUI and select Files > Services > Backup.