Date: Thu, 9 Aug 2001 22:13:06 -0400 (EDT) From: Jim Durham <durham@w2xo.pgh.pa.us> To: Alvin Sim <bsd140870@yahoo.co.uk> Cc: Christoph Sold <so@i-clue.de>, freebsd-questions@FreeBSD.ORG Subject: Re: Re[2]: backup server Message-ID: <Pine.BSF.4.21.0108092201530.89859-100000@w2xo.pgh.pa.us> In-Reply-To: <18015804014.20010805144238@yahoo.co.uk>
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On Sun, 5 Aug 2001, Alvin Sim wrote: > heya christopher, > > Sunday, August 05, 2001, 02:51:00 AM, Christoph Sold wrote: > > > Alvin Sim wrote: > >> > >> i'm looking into implementing 2 servers for a dept. and am looking for > >> ways to to "mirror" a server -- ie, if one fails, all clients will > >> automagically connect to the second server -- ala NT PDC's. > >> > >> what do i (basically) need to do/implement? any pointers to some > >> relevant docs would be great. thanks. > > > There is no such thing as the magic you describe. To get a little bit of > > this ideal solution, you'd have to define > > > > 1) which services this boxes have to provide > Samba 2.2.x (user authentication), Squid (proxy), IPFW (& NATD?) for > Internet access priviledges, Web-Caching, and maybe DNS. i'm sure there > are going to be a couple more services but this is basically the > basics/needed ones > > > 2) what the least acceptable working level of that service is > Samba and? DNS, since they need the user authentication for (domain) > logons and DNS to resolve? i'm not sure if this is what you meant by > 'least acceptable working level' > > > 3) how to detect the failure and > this is what i am looking into as well and i really can't answer this > one. i dont know if anyone that have done a lot of years of > administration knows when a server is going to make a boo-boo either. > maybe there is this someone and maybe he'll give me some pointers in > waht to lookout for :) but i really doubt it since there are basically a > lot of probable cause for a server to go down > > > 4) how to switch over that service safely to the second box. > i suppose this is the subject line. how does an NT server works in a DC > environment? basically, this is what i was thinking of doing but... how > do you make freebsd do something similar? (ie, synchronizing all datas - > if at all possible, which i doubt, at a certain interval time?) i dont > know, frankly. > > > each of those considerations is pretty complicated, and there is no such > > thing as a standard definition. Thus you have either to invest some time > > to think about it, or pay some amount of money to get somebody who does. > I have also thought about this a bit at our company. At lot depends on how "fancy" you want to get. A very workable system would be to have a 2nd server on a different IP, and do a tar using an "mtime" of 10 minutes (or whatever period) and output it through an NFS mount to the other system and untar it. This would transfer only what had recently changed to the other system. You could write a "watchdog" script to monitor the primary server from the secondary and initiate an ifconfig to the primary IP and a restart of Samba, etc on the new IP. Of course, there are many problems, like a partial failure of the primary that would be either difficult to detect, or would leave the primary running on it's IP and interfere with the new primary (the old secondary). Anyone who had a file open on Samba would get strange results! The only way to ensure a seamless transition would be to write everything to both servers all the time. I'm not aware of any way to do this, but maybe others are. Just some thoughts. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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