Efficient use of Docker containers for fuzzing

Question

I've been trying out various fuzzers (AFL, Nautilus, KLEE, etc) on different applications that take a file input and I was looking into pointing the "out" directory of these fuzzers (e.g. afl-fuzz -i in -o out ./app @@) to some sort of partition in memory (like ramfs). Is this necessary for these types of fuzzers? I'm concerned with all of the I/O to my disk for reading and writing files to send to the application.

I came across this answer to a similar question: Running Docker in Memory? They mentioned that you can use -v to accomplish this. But when I tried to mount the RAM disk using the -v option for the out directory, I saw a significant performance drop in executions/sec in AFL. This dropped from ~2000 execs/sec to ~100 execs/sec. I know this is not because of the RAM disk partition, because using -v without the RAM disk passed in yields the same poor performance. Currently I have been running the fuzzer and then copying the contents over after I stop it to improve the performance. Should I be concerned with the hit on my disk?