Hi
Pretty much the same here, I tested a Nginx setup + PHP app with a mounted volume and serving a basic page takes ~3 seconds whereas the same page loaded without the volume (as in the container) takes 216ms.
Client:
Version: 1.12.0-rc2
API version: 1.24
Go version: go1.6.2
Git commit: 906eacd
Built: Fri Jun 17 20:35:33 2016
OS/Arch: darwin/amd64
Experimental: true
Server:
Version: 1.12.0-rc2
API version: 1.24
Go version: go1.6.2
Git commit: a7119de
Built: Wed Jun 29 10:03:33 2016
OS/Arch: linux/amd64
Experimental: true