Date: Mon, 12 Aug 1996 09:26:21 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: michaelh@cet.co.jp (Michael Hancock) Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Load-balancing box Message-ID: <199608121626.JAA25431@phaeton.artisoft.com> In-Reply-To: <Pine.SV4.3.93.960812140023.7033A-100000@parkplace.cet.co.jp> from "Michael Hancock" at Aug 12, 96 02:10:02 pm
next in thread | previous in thread | raw e-mail | index | archive | help
> Cisco has a cool new product called LocalDirector that looks like the > perfect load balancing solution. > > The box has an Intel MB, P133, and 2 Intel 10/100 Ethernet cards. > > A designated IP number can be setup so that when it hits the box it > translates it to one of the IP addresses for the multiple servers sitting > behind it. Otherwise it just functions as bridge. > > When it dispatches the request to one of the servers it starts a timer to > measure the response time. It uses the response time statistics to > determine which server to dispatch the next request to. > > If a server goes down then it stops dispatching requests to it. > > How hard would it be to build something like this with FreeBSD? I think this is only marginally more useful than using DNS to set up cluster aliases. Specifically, it can react when one of the machines goes down (but how can it know?). The whole problem is that you connect to an address instead of a service in the first place -- this type of load balancing assumes all clients have statistically identical duration, and doesn't truly balance the load between the boxes. For example, if I have 3 boxes, and 300 incoming connections are made, and 200 of them leave, one box can have 100 connections and the other two can be idle. The fix is called "service anonymity" and requires a fundamental change in the way addresses get resolved/routed, and the ability to actively retarget session state (if any) from one server to another through consensus of the servers in the cluster. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199608121626.JAA25431>