Merge branch 'add-efs-warning-to-requirements' into 'master'

Adding EFS warning to requirements

See merge request gitlab-org/gitlab-ce!25754

doc/install/requirements.md

@@ -51,6 +51,8 @@ Apart from a local hard drive you can also mount a volume that supports the netw
 If you have enough RAM memory and a recent CPU the speed of GitLab is mainly limited by hard drive seek times. Having a fast drive (7200 RPM and up) or a solid state drive (SSD) will improve the responsiveness of GitLab.
+NOTE: **Note:** Since file system performance may affect GitLab's overall performance, we do not recommend using EFS for storage. See the [relevant documentation](../administration/high_availability/nfs.md#avoid-using-awss-elastic-file-system-efs) for more details.
+
 ### CPU
 - 1 core supports up to 100 users but the application can be a bit slower due to having all workers and background jobs running on the same core