Meta server: implement directory storage tiers range which can be set and used to implicitly set storage tier range for files within a common path prefix. By default the directory storage tiers range default to the highest tier 15. To change directory's storage tires range a variant of set replication RPC is used. Only "root" allowed change directory's storage tier range.Changing directory's storage tier range has no effect on the files and directories that already exist. When created, sub directories and files (unless specified explicitly) "inherit" parent directory storage tiers range. Store non default directories storage tiers range in checkpoint. Allow set file replication log entry to operate on directories.
Client library: implement set storage tier range QFS client method.
Tools: qfs tool implement -sstr (set storage tiers range) sub command. Display directories storage tiers range with qfs tool -astat and qfsshell stat sub commands.