SharePoint 2013 Search - Crawl returns no items

Environment:

• Windows 2008 R2 SP1
• SharePoint 2013 RTM
• You have created search topology manually via Powershell or AutoSPInstaller and definded the -rootdirectory property when creating Index component.

Problem:

Search reports no errors - all services are healthy and reporting green.
Crawl does not return any items
Crawl log error message is: "The filtering process has been terminated"

Cause:

When the location of index is moved from default (C:\Program Files\Microsoft Office Servers\15.0\Data\Office Server\Applications)  the "WSS_WPG" group don't get the right permissions set on that folder.  The search account is a member and hence cannot create the files and folders needed.

Solution:

Give "WSS_WPG" group "Full control" on "C:\Program Files\Microsoft Office Servers\15.0\Data\Office Server\Applications" subfolders and files.