EasyEngine is moving to Redis for caching (a replacement for Memcached); in that world the config would be:
EasyEngine site with --wpredis switch
It’ll install Nginx-Helper and config it to use Redis
You can then use Redis Object Cache Plugin which replaces a lot of what W3TC / APC etc
There’s probably no need for varnish in front of the full caching that EasyEngine does. Varnish is a proxy cache that stands in front of other httpd services (nginx is actually a proxy as well, but can serve as the main httpd as well).
So basically just create your sites (or convert) with --wp --wpredis and you should be good to go. You’ll need to decide if you want HHVM or not. To convert an existing site do
ee site update example.com --wp --wpredis
Note, converting will remove W3TC so if you are using that to rewrite CDNs or minification you’ll need to plan for that.
We don’t use ISPConfig for our needs, so not much help there. In general we’d rather not burden our VPSs with GUI / Front end tools to admin the sites, they just take resources away from the sites. However, it is pretty straight forward from testing we’ve done.
To Answer your specific questions
- Probably just Redis; i.e. --wpredis
- Here’s a quickie:
- memcached - in memory key value store
- redis - more advanced in memory key value store
- APC - memcached or redis can replace this; this is an opcache which caches the intermediate processed php code
- varnish - proxy server in front of other web servers, with EE don’t need really unless you do some really advanced clustering / load distribution type servicing. Nginx or Apache with process a page and produce output. Varnish with store the resulting output and send that to a client instead of asking nginx or apache to do it. However, nginx with what EE has done is very good at this as well, so unless you really have some advanced scenarios there’s no need.
- Redis is probably the way to go going forward
- Decision here if you want HHVM or PHP-FPM; RT has done good work to have HHVM with PHP-FPM fall back so provided you have no plugin issues HHVM is probably good (note, PHP 7 may change this).
- Also decide if you want Redis Object Cache - if you have memory capacity go for it
- Probably for best performance you want an HHVM, Redis with Redis Object Cache site. That’s all. RT says there’s no need for a db cache as MySQL does a good enough job. No need for varnish proxy cache.
Hope this helps - much of this depends on more specifics of the types of sites you’re operating and the amount of memory / processing on your specific VPSs.