Hello Peter,
Thanks for the feedback. From my experience enabling the nginx options in plesk significantly reduces performance as measured by
https://developers.google.com/speed/pagespeed/insights/.
I'm fairly new to plesk (2+ years, versions 12.08, 12.5.30, 17.07) and have seen this performance drop consistently across the last 2 versions (do not recall if this was an issue with 12.0.8).
To put some hard numbers on this I just did some tests on live sites:
Wordpress (w/2017 theme) dropped from 89%/95% to 71%/74%. That's an 18% and 21% performance drop! (standard wordpress .htaccess file)
Joomla! (custom theme) dropped from 75%/91% to 59%/72% (16% & 19% performance drop) (custom .htaccess file)
Using the standard joomla! .htaccess file the numbers are 71%/87% and drop to 57%70% with nginx smart option. (14% &17% performance drop)
This is with "Smart static files processing" enabled. "Serve static files directly by nginx" did not seem to make any significant difference in any testing.
This is easy to reproduce 100% of the time:
1. Install plesk 17
2. Install latest version of wordpress
3. PageSpeed Test (site is slower)
4. Plesk | Domain to test | Apache & nginx Settings | Uncheck "Smart static files processing", Uncheck "Serve static files directly by nginx" | Apply
5. Retest in PageSpeed (performance improves significantly).
With this test, we can rule out wordpress or joomla! extensions/plugins, .htaccess files, 3rd party plesk addons, etc.
When I first discovered this I thought I was dealing with a simple configuration issue. I changed the PHP handlers, PHP versions, with and without .htaccess files and the only common element was the nginx "Smart static files processing" option.