Our premium servers have been running on Varnish for over two months now with no issues. The issue is not related to Varnish, however it is exacerbated by Varnish's Timeout settings with regard to Litespeed, an Apache Drop-in Replacement that is in use on our free servers. A similar implementation was tested on free hosting, and worked fine. There were unexpected, outside events that we found out were causing issues on xo1, xo2, and xo3. A fix was tested on one server, and showed good results, and was then deployed to the other two servers yesterday--just as the server status page says.
Last night, after reviewing monitoring logs, we found out that the issue was not fully resolved, and we began investigating other solutions.
Around 4AM Eastern time, after testing, we deployed a fix onto XO1, which has shown good results since the deployment. We are working on deploying the patch to xo2 and xo3--which will happen shortly.
The new implementation of Varnish and Apache utilizes a custom-built Litespeed SAPI that processes PHP, and in our testing, has shown speeds to be at least an order of magnitude faster than Litespeed alone, and almost two orders of magnitude faster than Apache alone.
It is very difficult to test and make large-scale changes to free hosting servers, because any small change affects so many accounts, and therefore changes take a very long time to put in place, and have to be planned out and tested in a smaller-scale. A good chunk of time last night was spent waiting for our security system, CageFS, to propagate file system changes into every user's account.
The free hosting servers are not guinea pigs for our premium hosting--nor are the users of free hosting. That being said, free hosting should not, and never should have been considered a "Free trial" of sorts of Premium hosting--they're incomparable, for many reasons.
We strive to provide the best service for all of our customers, both free and paid. We have a dedicated staff that works constantly to provide an amazing service for all of our users and customers alike--we don't put one group in front of another. Threatening to leave, or to not upgrade does not sway us in any way to put through untested resolutions for problems. In fact, most of our clients these days are not from upgrades from Free hosting. We provide our hosting for free as a courtesy, and because it's what we've been doing for the past ten years.