Converting Volume Replication Type (High Throughput to Low Latency)

A low latency replication type allows for volumes to be replicated on multiple containers (in parallel) from the master container.

Note: Contact MapR Support before converting volumes to low_latency replication type.

To convert from a high-throughput to a low-latency replication type:

  1. Change the permissions on the volume from read-write to read only.
    For example:
    maprcli volume modify -name mvol1,mvol2 -readonly true
    Wait for the running operations to complete before proceeding to the next step.
  2. Convert the volume from high_throughput replication type to low_latency replication type using the maprcli command.
    For example:
    maprcli volume modify -name mvol1,mvol2 -replicationtype low_latency
    Wait till replication type conversion is complete and all the containers of the volume acquire a master. If necessary, run the following command to see if replication type has been converted:
    maprcli volume list -columns ReplTypeConversionInProgress,volumename
    If the conversion is complete, the ReplTypeConversionInProgress flag will be set to false (0). For example, the 0 in the ReplTypeConversionInProgress column in the following sample output indicates successful conversion of corresponding volume in the volumename column:
    # maprcli volume list -columns ReplTypeConversionInProgress,volumename
    ReplTypeConversionInProgress  volumename                                                                                                              
    0                             mapr.apps                                                                                         
    0                             mapr.cldb.internal                                                                                
    0                             mapr.cluster.root                                                                                 
    0                             mapr.configuration                                                                                
    0                             mapr.hbase                                                                                        
    0                             mapr.jobtracker.volume                                                                            
    0                             mapr.metrics                                                                                      
    0                             mapr.node-20.lab.local.audit                                                                      
    0                             mapr.node-20.lab.local.logs                                                                       
    0                             mapr.node-20.lab.local.mapred                                                                     
    0                             mapr.node-20.lab.local.metrics                                                                    
    0                             mapr.node-20.local.audit                                                                          
    0                             mapr.node-20.local.logs                                                                           
    0                             mapr.node-20.local.metrics                                                                        
    0                             mapr.node-21.lab.local.audit                                                                      
    0                             mapr.node-21.lab.local.logs                                                                       
    0                             mapr.node-21.lab.local.mapred                                                                     
    0                             mapr.node-21.lab.local.metrics                                                                    
    0                             mapr.node-22.lab.local.audit                                                                      
    0                             mapr.node-22.lab.local.logs                                                                       
    0                             mapr.node-22.lab.local.mapred                                                                     
    0                             mapr.node-22.lab.local.metrics                                                                    
    0                             mapr.node-23.lab.local.audit                                                                      
    0                             mapr.node-23.lab.local.logs                                                                       
    0                             mapr.node-23.lab.local.mapred                                                                     
    0                             mapr.node-23.lab.local.metrics                                                                                                                                      
    0                             mapr.opt                                                                                          
    0                             mapr.resourcemanager.volume                                                                       
    0                             mapr.tmp                                                                                          
    0                             mapr.var                                                                                          
    0                             mvol1                                                                                             
    0                             mvol2                                                                                             
    0                             mvol3                                                                                             
    0                             users                                                                                             
    0                             vol3 
  3. Reset the permissions on the volume to read-write.
    For example, to reset, run the following command:
    maprcli volume modify -name vol1,vol2 -readonly false