ROOT 6.28/04 on a Ubuntu 18.04 LTS / x86_64 machine (with 1 Gb/s ethernet, the wget reported 10 MB/s downloading speed for the “test_ntuples_200123.root” file) …
[...]$ time root -b -l -q https://cernbox.cern.ch/remote.php/dav/public-files/1Cy1HIf03Ca76Dm/test_ntuples_200123.root
Attaching file https://cernbox.cern.ch/remote.php/dav/public-files/1Cy1HIf03Ca76Dm/test_ntuples_200123.root as _file0...
(TFile *) 0x55c224c3b950
real 0m8.699s <- 9 seconds to open a 4.5 MB file !!!
user 0m0.425s
sys 0m0.122s
[...]$ time root -b -l -q https://cernbox.cern.ch/remote.php/dav/public-files/1Cy1HIf03Ca76Dm/test_ntuples_200123.root -e 'Electrons_All->Draw("pt__NOSYS");'
Attaching file https://cernbox.cern.ch/remote.php/dav/public-files/1Cy1HIf03Ca76Dm/test_ntuples_200123.root as _file0...
(TFile *) 0x55d006f19b10
Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
real 3m34.464s <- WTF ???
user 0m0.899s
sys 0m0.226s