How does RSYNC "verify" integrity of a backup???

mdgm wrote:
You do an incremental backup. It compares the files on the source and destination. If the files are different (I.e. checksum doesn't match) the changes will be transferred across.

First, THANKS SO MUCH for the fast response!!!

So, you are saying the (first) RSYNC backup (after the initial full backup/transfer of data) does a checksum verification on each file (source versus target) to determine if two same-named files are different?

I am not clear on this because several posts on this forum state that RSYNC uses timestamp/filesize to determine if a file (between source and target) has changed, then if a difference is detected, RSYNC does the delta calculation to determine what delta gets backed up.

Here is one such post:
viewtopic.php?f=31&t=27318&p=152960

ewok wrote:
bru wrote: What I want to happen is for rsync to compare dates and checksums of the file and to not backup files that have not changed so that the network does not get hit very hard and the disks to not get too much usage. That's what rsync does, using timestamp and filesize to check if a file needs to be transferred. Using checksums would be very slow....