Promising results with the log2ram rsync modifications you suggested @pb66
rsync -aXv --inplace --no-whole-file --delete --links $RAM_LOG/ $HDD_LOG/ 2>&1 | $LOG_OUTPUT
brings it down to ~11 sectors/minute 0.09 kb/s, in the previous 6 hours before the modifications, the write rate had increased to 0.86 kb/s so a 10x reduction.