Renaming (with 'mv') very large files is SLOW

[cygwin@kosowsky.org]

René Berber wrote at about 09:13:59 -0600 on Monday, January 31, 2022:
 > On 1/31/2022 8:59 AM, Eliot Moss wrote:
 > 
 > > On 1/31/2022 9:52 AM, cygwin@kosowsky.org wrote:
 > 
 > >> I tried renaming some very large files (20-40 GB) using: mv
 > >> <oldname> <newname> without changing the directory of course.
 > >> 
 > >> The process took about 10-20 minutes with Task Manager showing
 > >> disk activity of 100+ MB/s.
 > >> 
 > >> Is there something about such large 'renaming' that actually
 > >> results in the file being really moved (aka copied) rather than
 > >> just renamed?
 > > 
 > > The two places are probably on different volumes (loosely, different
 > >  disks). That requires a physical move, even under Linux.  Your
 > > volumes seem a bit slow to access - is one perhaps across a slow
 > > network?  The rates you cite suggest movement of 50Mb/s (50Mb read +
 > > 50Mb write = 100Mb overall).  For 40 Gb that should take 40Gb / 50Mb
 > > = about 820 secs = a little under 14 mins.
 > > 
 > > (When I say your volumes are slow, I speak from the luxury of having
 > > a 2Tb solid state drive!  Actually, those speeds may be reasonable
 > > depending on the nature of your system.)
 > > 
 > > If the two locations are on different drives, there's no real
 > > avoiding this.
 > 
 > Nope, I've also complained about this (long ago), if the two locations
 > are the same remote drive... Cygwin moves the entire file over the network.
 > 
 > I ended up writing my own Samba mv command.
 > -- 

In my case the directory (where I renamed the file) is on my C-drive.