Another data point. For me it actually takes 1m26s for a mounted volume in OSX vs 1s for non mounted. And 12s mounted vs 0.65s non-mounted with docker-machine:
Docker for Mac:
docker run --rm -it -v `pwd`:`pwd` -w `pwd` alpine /bin/sh
/Users/stefanfoulis/tmp/speedtest # time dd if=/dev/zero of=test.dat bs=1024 count=100000
100000+0 records in
100000+0 records out
real 1m 26.05s
user 0m 0.17s
sys 0m 2.44s
/Users/stefanfoulis/tmp/speedtest # cd /
/ # time dd if=/dev/zero of=test.dat bs=1024 count=100000
100000+0 records in
100000+0 records out
real 0m 1.06s
user 0m 0.06s
sys 0m 0.91s
pinata diagnose
OS X: version 10.11.4 (build: 15E65)
Docker.app: version v1.11.0-beta6
Running diagnostic tests:
[OK] docker-cli
[OK] Moby booted
[OK] driver.amd64-linux
[OK] vmnetd
[OK] osxfs
[OK] db
[OK] slirp
[OK] menubar
[OK] environment
[OK] Docker
[OK] VT-x
Docker logs are being collected into /tmp/20160413-150849.tar.gz.
docker-toolbox / docker-machine
docker-1.10.3 run --rm -it -v `pwd`:`pwd` -w `pwd` alpine /bin/sh
/Users/stefanfoulis/tmp # time dd if=/dev/zero of=test.dat bs=1024 count=100000
100000+0 records in
100000+0 records out
real 0m 12.25s
user 0m 0.08s
sys 0m 6.50s
/Users/stefanfoulis/tmp # cd /
/ # time dd if=/dev/zero of=test.dat bs=1024 count=100000
100000+0 records in
100000+0 records out
real 0m 0.65s
user 0m 0.04s
sys 0m 0.61s