Rsync just hangs..

Holger Ohmacht aka h8ohmh / 8ohmh:

The problem lies in the filesystem buffer / usage of the interworking of harddisk/hw so far as I could investigate.

Temporal solution for local drives (eg. USB3<->HD) : A script which is polling the changing disk space. If no changing free disk space then rsync is stalled and have to be restarted

    cmd="rsync -aW --progress --stats --preallocate --super <here your source dir> <here your dest dir>" 
    eval "$cmd" &  
    rm ./ndf.txt rm ./odf.txt 
    while [[ 0 == 0 ]]; do
            df > ./ndf.txt
            cmp ./odf.txt ./ndf.txt
            res="$?"
            echo "$res"
            if [[ $res == 0 ]]; then
                    echo "#################################################"
                    ls -al "./ndf.txt"
                    ls -al "./odf.txt"
                    killall rsync
                    eval "$cmd" &
            else
                    cp ./ndf.txt ./odf.txt
            fi
            sleep 60 
    done

`
Change `<source dir>` etc to your paths!

In my case it is always stalling after some few 100's files  by usage of rsync's --preallocate option  files (normally because of better disk performance and rescueing continuous blocks), so as long as the disk and filesystem drivers not reworked there just this solution