Date: Fri, 10 Aug 2001 16:04:34 -0500 From: Tony Wells <tony@camel.kdsi.net> To: Jim Durham <durham@w2xo.pgh.pa.us> Cc: Duncan Sayers <duncan@apdata.com.au>, freebsd-questions@FreeBSD.ORG Subject: Re: backup server Message-ID: <3B744C62.7F4333E2@camel.kdsi.net> References: <Pine.BSF.4.21.0108101537440.95280-100000@w2xo.pgh.pa.us>
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Jim Durham wrote: > > On Fri, 10 Aug 2001, Duncan Sayers wrote: > > > On Thu, 9 Aug 2001, Jim Durham wrote: > > > > > On Sun, 5 Aug 2001, Alvin Sim wrote: > > > > 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. > > > > > > > > How about using rsync in a script run by cron at specified intervals to > > synchronise files from one server to another. To quote the man page: > > > > "The rsync remote-update protocol allows rsync to transfer just the > > differences between two sets of files across the network link." > > > > Then you could have a replicated server (give or take a couple of > > minutes of changes, depending on the sync interval), to which you could > > cut over to if your "main server" croaks > > > > -- > > I wasn't familiar with it, but I found it in ports and read the > package description. Sounds interesting, but if it is a cousin > of rcp, it's probably unsafe in a secure environment as you would > have to run portmap and rstatd. I'd feel better if it were using > scp instead of rcp 8-) . It will connect over several different protocols, one of which is ssh. We use it over ssh and it works great. > > -Jim > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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