log a rsync mistake

I want to sync some files from 2 directories mirror1 andmirror2.So I run:

nohup rsync <src>/mirror1 ./tmp -a --delete &
nohup rsync <src>/mirror2 ./tmp -a --delete &

the argument --delete would delete all the file not exist in source directories. So only second command make effect.

Avoid abusing of --delete when using rsync.