On Thu, Apr 19, 2012 at 3:48 PM, Joel Svensson <joel__svens...@hotmail.com> wrote: > Hi! > > From the text below I can't figure out if HAProxy will handle more sessions > (than ~20000/GB ram) in Layer4 mode? > > The session concurrency > This factor is tied to the previous one. Generally, the session rate will > drop when the number of concurrent sessions increases (except the epoll > polling mechanism). The slower the servers, the higher the number of > concurrent sessions for a same session rate. If a load balancer receives > 10000 sessions per second and the servers respond in 100 ms, then the load > balancer will have 1000 concurrent sessions. This number is limited by the > amount of memory and the amount of file-descriptors the system can handle. > With 8 kB buffers, HAProxy will need about 16 kB per session, which results > in around 60000 sessions per GB of RAM. In practise, socket buffers in the > system also need some memory and 20000 sessions per GB of RAM is more > reasonable. Layer 4 load balancers generally announce millions of > simultaneous sessions because they don't process any data so they don't need > any buffer. Moreover, they are sometimes designed to be used in Direct > Server Return mode, in which the load balancer only sees forward traffic, > and which forces it to keep the sessions for a long time after their end to > avoid cutting sessions before they are closed. > > > Regards, > Joel >
Hi Joel, I guess that by layer4 mode, you mean tcp mode. Unfortunately, when Willy speaks about layer 4 load-baancers in the text above, he speaks about LVS like load-balancers and why in HAProxy you can have "only" thousends of connections while LVS like LBs can annouce millions... So in haproxy, whatever the mode, tcp or http, you'll always have thousends of connexions. cheers
