The point is your example. 1000 req can cause in practice 10000 memcache req. So if you want scale 5 times not only the number of ports on your (one/one) machine setup will hit a hard limit.
Both services on the same machine is also difficult.pppppppppppp Henrik Schröder <[email protected]> schrieb: >On Fri, Feb 10, 2012 at 09:21, Yiftach Shoolman ><[email protected]>wrote: > >> TIf you but the Memcached on a dedicated server each webserver only deals >> with the network I/O associated with its traffic, leaving the dedicated >> Memcached server to deal with all cached traffic. >> > >You are still not making any sense. Let's say you have two machines, that >you need to handle 1000 web requests, and that each web request results in >a memcached request. > >If you split it like you suggest and put a webserver on one machine, and >memcached on the other machine, then the webserver will need to handle 1000 >web requests, and the memcached server will need to handle 1000 memcached >requests. > >But if you don't split it like I suggest, and you put a webserver on each >machine and memcached on each machine, then each webserver will need to >handle 500 webrequests, but only 250 of those need to talk to memcached >over the network, the other half talk to the local memcached and generate >no network traffic. > >So if you don't split them, there will be 500 memcached requests less over >the network, which means you scale better. Not to mention the fact that >you're using RAM you probably wouldn't use otherwise, and that you lose >less of your cache if one server goes down. > > >> To clear it more, if you have N servers each deployed with a webservers a >> memcached server, and memcached is distributed across all servers, each >> webservers needs to deal with Memcached network I/O associated with N-1 >> webservers --> we found it architecturally wrong, it actually slows down >> the entire application >> > >So what? The number of servers you send requests to matters very little, >it's the total amount of requests that's interesting. One webserver sending >1000 requests to one memcached server is the same as one webserver sending >100 requests to 10 different servers. It's still 1000 requests? > > >/Henrik
