Today we hit a new low in server responsiveness, but cause is unknow: traffic was the same as always, no major content was published and visited, no anormal processes were running... I'm still reading logs to find a reason...
Also, I spent just a little time in reading Varnish documentation and testing elsewhere: still some issue about cache management, but I think next week I can run it on main server. All of you will be alerted and asked to report me about undesired behaviours, I expect your collaboration 