A GPFS tiebreaker disk can be changed only when the DB2 pureScale cluster is in maintenance  mode. 

To monitor the progress of adding and removing disks and GPFS rebalancing, run the GPFS mmdf  <file system> command. 

## Related information 

Changing the physical disk storage of GPFS file systems:  http://www.ibm.com/support/docview.wss?uid=swg21633330 

GPFS mmdf command reference:  https://ibm.biz/BdrLeX 

