Hadd and tree size limitation


I’m merging several ROOT files with trees using hadd. I expect the output file to be about 100 GB, so I set the maximum tree size much bigger than this value (1e+18 bytes = 1E+9 G):

TFile file("out.root", "recreate"); TTree tree("T"); tree.SetMaxTreeSize(1e+18);
However, the program switches to a new file _1.root already when the file size exceeds approx. 11 G, which does not allow me to merge all the files in a single file. Why?

The file system I’m using is ext3, so it should not be due to the OS limitation.
My ROOT version is 5.25/02,

Move to version 5.26 where the default tree size is set to 100 GBytes