Messages in this thread |  | | From | "James R. Leu" <> | Subject | mirrored machines via network | Date | Fri, 1 Nov 1996 16:23:52 -0600 (CST) |
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First off please let me apologize for my lack of kernel programming knowledge, this is my first venture into kernel space. My basic goals of this letter are 1) a reality check and 2) to obtain a list of resources of where to look or what to read to get me started.
As my title below states I'm in charge of administrating all the network operations of a small ISP. I am looking into ways of implementing redundant servers. By this I mean two machine that are exactly the same as far as services provided, and data stored. There only deviation would be the IP address assigned to it. My example will hopefully reveal why I want to achieve this.
The idea I have, necessitates two main developments. The first of which is a "intelligent" name-server. I have begun development of this already. I have started by using th bind-4.x.x source. The end result will hopefully be a name-server that checks if a machine is responding, before it gives out the IP address. The second of which is the "mirrored machines via the network". Because of my limited knowledge of kernel I/O I'm not really sure how to implement such a driver/service. My initial looks into the I/O subsystem led me into the drivers/block directory of the Linux kernel source. I look at hd.c and could understand what was happening, but I don't understand how it fits in to the whole scheme of things.
The best way to illustrate how the entire system would work would be to give an example. I will refer to the primary machine as machine A, and the backup machine as machine B. There is at least a third machine on the network, and this operates as the primary DNS for the network. Under normal situations (ie no failed hardware, no kernel panics :o) machine A response to all WWW services all e-mail services, and all authentification requests and usage accounting (via RADIUS). The machine also serves shell logins. During this time machine B needs to constantly be updates to account for changes in web pages, changes in passwords, in general all changes to the file system on A need to be duplicated on B. The reason it needs to be duplicated arises when machine A blows up. At this time the primary name server would notice that machine A is not responding correctly. It would switch its internal tables for machine A and now point them to machine B.
I do realize there are many areas that need to be worked out. The least of which is how to determine if a machine is no longer responding, but I hope with some input from this community, to be able to overcome each problem and form a truly reliable solution. I welcome all responses/tips/hints/flames.
Last but not least, if anyone has seen this or anything similar, please let me know. I looked long and hard for something similar, but I'm sure my search was not entirely exhaustive. Also I know my view of this may be naive, so please do enlighten me.
James -- James R. Leu Network Administrator CORE Digital Communication Services jleu@coredcs.com
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