There are 3 main syncing methods
- no flags - (size, modtime)
--size-only(size)--checksum(size, checksum)
Then there are the modifiers
--ignore-sizemakes all of the above skip the size check--ignore-times- uploads unconditionally (no checks)
Just in case you are wondering where these flags came from - they are all from rsync...
--ignore-times only works for uploads, it isn't implemented for check.
I hope that helps!