For p4d 2011.1 thru 2015.1, set rpl.compress=3. For p4d 2015.2+, set
rpl.compress=4. A value of 4, new in P4D 2015.2, compresses journal
data only, which is almost always advantageous as it compresses well,
while avoiding compression of archive data, which is a mixed bag in
terms of performance benefits, and potentially a net netagive.