Parallel cloning for Clone-Controlled Replication (CCR)

Environment:

EMC NetWorker

EMC Data Domain

 

 

Description:

Parallel cloning is an enhancement to clone-controlled replication (CCR) for Data Domain systems that allows clone operations to occur concurrently, similar to save operations, so that multiple clone threads can occur in parallel for each clone process. NetWorker enables this feature by default, and allows up to 30 parallel cloning sessions per NSR clone operation.


Resolution:

 

Modifying parallel save set cloning sessions

NetWorker spawns a maximum of 30 parallel cloning sessions per NSR clone operation.  You can use the nsrcloneconfig file to modify the number of parallel cloning sessions for Clone Controlled Replication (CCR) clones only.

 

Note, however, that If the number of save sets exceeds the maximum, NetWorker queues the remaining save sets until a session becomes available. You should only modify the default settings if they are problematic for your system.

 

Follow these steps to modify the number of parallel cloning sessions.

 

1. Create the nsrcloneconfig file on the machine that runs the NSR clone process under the following locations:


•On Windows: C:\Program Files\EMC NetWorker\nsr\debug
•On UNIX: /nsr/debug

 

Note: The nsrcloneconfig file should not have an extension.
 

2. Type the following parameters in the nsrcloneconfig file to modify parallel cloning:


•To use global settings:

max_threads_per_client=max concurrent save sets

max_client_threads=max clients

where:

– max concurrent save sets is the maximum number of save sets the Network host that initiates the NSR clone process concurrently clones for a particular client.  The number must not produce a value greater than 30 when multiplied by max clients.

– max clients is the maximum number of unique clients that are involved in the parallel cloning session. The number must not produce a value greater than 30 when multiplied by max concurrent save sets.

•To use settings for a specific clone resource:

nsrclone_resource_name_max_threads_per_client=max concurrent save sets

nsrclone_resource_name_max_client_threads=max clients

where:

– nsrclone_resource_name is the name of the clone resource that the custom settings apply to.

– max concurrent save sets is the maximum number of save sets the Network host that initiates the NSR clone process concurrently clones for a particular client.  The number must not produce a value greater than 30 when multiplied by max clients.

– max clients is the maximum number of unique clients that are involved in the parallel cloning session. The number must not produce a value greater than 30 when multiplied by max concurrent save sets.

 

For example, to involve 15 clients and have 2 save sets initiated for each client for the clone resource TestClone only, type the following parameters:

TestClone_max_threads_per_client=2

Testclone_max_client_threads=15

 

Note: If you use both settings, the specific settings override the global settings.
 

3. To enforce sequential cloning, type the following parameters:


•To use global setting:

max_threads_per_client=0

max_client_threads=0


•To use settings for a specific clone resource:

nsrclone_resource_name_max_threads_per_client=0

nsrclone_resource_name_max_client_threads=0

 

Where nsrclone_resource_name is the name of the clone resource that the custom settings apply to.
 

Note: If you use both settings, the specific settings override the global settings.


4. Optionally, use the log messages in the clone log files that are created for each cloning operation to cross-verify the number of sessions. The files are under the following locations:


•On Windows: C:\Program Files\EMC NetWorker\nsr\logs\clone
•On UNIX: /nsr/logs/clone


Cloning multiple backup pools with parallel cloning

You can use parallel cloning with multiple backup pools. However, NetWorker cannot clone save sets from multiple backup pools in parallel.

Parallel cloning occurs only for save sets that are read from the same pool. When you attempt a clone operation for save sets that are read from more than one pool, NetWorker queues the backup pools. The clone operation clones the save sets from one pool before proceeding to the next queued pool.

To clone save sets from multiple backup pools simultaneously, you must use a separate NSR clone process for save sets that come from each backup pool.

 

Reference:

EMC Support Solution Number: 188548