rsync question

[Rashkae]

On 13-12-12 09:50 AM, R Kimber wrote:
> I've been using rsync to create an exact backup copy of my music
> collection onto another disk.  I recently decided that I wanted to change
> the directory structure of the collection and, to prevent rsync having to
> spend hours deleting and copying the large files between the disks, I spent
> some time making the changes manually on each disk.  However, the next time
> the backup script ran rsync it ran for five hours.  The two disks were identical.
> So what was it doing?  Or, rather, what was I doing wrong? I've clearly
> misunderstood rsync. I thought that if it saw two identical file structures
> it wouldn't actually do very much other than make a note of the new
> structure, which even for half a TB shouldn't take all that long.
>
> - Richard.

The last modified time stamps were different.  When copying over a 
network protocol, (rsync or rsync through ssh), rsync would compare each 
affected file and only transfer over the data needed to for any 
differences/discrepencies.  However, when synching between locally 
mounted filesystems, if the file timestamps are different, the file is 
simply copied over, (presumably, copying the file doesn't require any 
more disc activity than comparing both byte for byte.)

Renaming or moving folders should not have changed any timestamps... did 
you end up copying directories/files instead while you were re-organizing?

5 hours for 500GB, roughly 30MB/s... drive connected by USB? (Offtopic, 
but I thought 5 hours sounded too slow, until I did the math.)