The POSIX translator is now enhanced with an option that allows user to reserve disk space on the bricks. Some administrative operations, like expanding storage or rebalancing data across nodes, require spare working space on the disk. The storage.reserve option lets users expand disk or cluster when backend bricks are full.
When the bricks have free space less than or equal to the reserved space, as declared by the user, new files are not created. This prevents ENOSPC errors on mount points.
To enable reserve option, execute the following command:
# gluster volume set volname storage.reserve percentage
Once this option is enabled, the reserved disk space is not used by the mount points. The
storage.reserve option either takes a percentage(%) suffixed value or an unsigned integer value suffixed with absolute units(KB, MB, GB etc). The default value for the option is 1%(1% of the brick size). If set to 0 this option is disabled.
When the disk space reduces to the size of reserved disk space, only internal operations like rebalance, self-heal and so on can be performed.