l am just using kosmosfs,but l find several problems
1.after Rename(old.c_str(), new.c_str()), call the function Exists (old.c_str),lt returns true
but the old file have already  be renamed 
2 after creat a dir and two file in the dir,l write something into one of the file,then call the 
function GetDirSummary,but lt shows both numfiles and numBytes  are  zero
3 l don't know if l misuse  the function UpdateFilesize after l write something into one file,
the size returned is always zero,  whether the function works only if multiple client write to the some
file,and the function was used to indicate how much data be wrote by other clients not considering 
bytes wrote itself?

thank you for  the answers kindly