Thread: [Fwd: 2 computers 1hd 2 postgres daemons. Is it possible?]
-- Joseph Shraibman jks@selectacast.net Increase signal to noise ratio. http://www.targabot.comKris Klindworth wrote: > > > "Clark, Joel" wrote: > > > > > > Yeah, I was really just curious if the proposed system was at a system leve > > l > > > or a network level. Having two physical machines share (at the system i/o > > > level) a storage unit is something I have never heard of. Does such a beas > > t > > > exist? > > > > Yeah, they exist, though why they exist is beyond me. Maybe because > > windows systems crash all the time. It doesn't make much sense to me, > > after all it would seem that hard drive failure happens more often that > > the system crashing for no reason. > > It is a down time issue. We can't afford to be down for hours at a time > when a chip fails. It doesn't happen often, but it does happen and when > it does it is a VERY big deal. > > We have two identical boxes that provide two distinct service sets. > The two machines and the drives for their services are on a shared > SCSI bus. In normal mode, the drives are mounted on their normal hosts > and the systems monitor each other. If one sees that the other has gone > down, it will automatically mount the drives for the missing services, > start up the applications, and we are back in business with zero manual > intervention. It just sends out an email warning us that the other > system went down and that it had taken over the services. When the > repairs are completed on the downed box, we pick a convenient time to > interrupt the services and then we move them back to their normal host. > Then you run into problems with both systems failing to detect the other and thinking it is the only one left running, so you end up with two servers running. My point is that I can't conceive of a failure that is likely to happen where a shared scsi bus makes a difference. If a hard drive goes down it is no help. If the application software goes down it doesn't help because they share the same application code. I would think the added complexity of a shared scsi bus would create more failures than would happen on a normal system from a hardware chip failing or something. But then again what do I know? -- Joseph Shraibman jks@selectacast.net Increase signal to noise ratio. http://www.targabot.com
Granted it probably not the most efficient solution, but if it is something that is really a problem... what about having your dual server, one data source setup, but the second server is idle and does nothing and only kicks in if the primary drops? Might be more complicated to setup than it sounds and there still would be a time delay for the second to pick up, but it technically would eliminate the two servers butting heads. Again though, not very efficient solution... unless it is very critical and money is no object. :) Adam Lang Systems Engineer Rutgers Casualty Insurance Company ----- Original Message ----- From: "Joseph Shraibman" <jks@selectacast.net> To: <pgsql-interfaces@postgreSQL.org> Sent: Tuesday, October 17, 2000 2:53 PM Subject: [Fwd: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it possible?] > > -- > Joseph Shraibman > jks@selectacast.net > Increase signal to noise ratio. http://www.targabot.com
And there DOES come a time where PostgreSQL is not the correct solution. At this time you can not mirror a postgreSQL server like you can mirror a, say Oracle server. It sounds like they want mirroring servers the way some commerical servers can do. Nothing stopping your employer/patron/slave driver from paying someone to develop this kind of feature in postgreSQL. And nothing stopping you from re-writting the app such that the app worries about mirroring the data. (IE, it makes sure it has its own transaction set in case it can't talk to the other server, and all queries are duplicated on the other box.) On Tue, 17 Oct 2000, Adam Lang wrote: > Granted it probably not the most efficient solution, but if it is something > that is really a problem... what about having your dual server, one data > source setup, but the second server is idle and does nothing and only kicks > in if the primary drops? Might be more complicated to setup than it sounds > and there still would be a time delay for the second to pick up, but it > technically would eliminate the two servers butting heads. Again though, > not very efficient solution... unless it is very critical and money is no > object. :) > > Adam Lang > Systems Engineer > Rutgers Casualty Insurance Company > ----- Original Message ----- > From: "Joseph Shraibman" <jks@selectacast.net> > To: <pgsql-interfaces@postgreSQL.org> > Sent: Tuesday, October 17, 2000 2:53 PM > Subject: [Fwd: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it > possible?] > > > > > > -- > > Joseph Shraibman > > jks@selectacast.net > > Increase signal to noise ratio. http://www.targabot.com > >
I guess you missed the announcement. This *is* coming to postgres, but I'm unclear if it is going to be included or it will be a seperate package. Marc Rassbach wrote: > > And there DOES come a time where PostgreSQL is not the correct solution. > > At this time you can not mirror a postgreSQL server like you can mirror a, > say Oracle server. It sounds like they want mirroring servers the way > some commerical servers can do. > > Nothing stopping your employer/patron/slave driver from paying someone to > develop this kind of feature in postgreSQL. > > And nothing stopping you from re-writting the app such that the app > worries about mirroring the data. (IE, it makes sure it has its own > transaction set in case it can't talk to the other server, and all queries > are duplicated on the other box.) > > > On Tue, 17 Oct 2000, Adam Lang wrote: > > > Granted it probably not the most efficient solution, but if it is something > > that is really a problem... what about having your dual server, one data > > source setup, but the second server is idle and does nothing and only kicks > > in if the primary drops? Might be more complicated to setup than it sounds > > and there still would be a time delay for the second to pick up, but it > > technically would eliminate the two servers butting heads. Again though, > > not very efficient solution... unless it is very critical and money is no > > object. :) > > > > Adam Lang > > Systems Engineer > > Rutgers Casualty Insurance Company > > ----- Original Message ----- > > From: "Joseph Shraibman" <jks@selectacast.net> > > To: <pgsql-interfaces@postgreSQL.org> > > Sent: Tuesday, October 17, 2000 2:53 PM > > Subject: [Fwd: [INTERFACES] 2 computers 1hd 2 postgres daemons. Is it > > possible?] > > > > > > > > > > -- > > > Joseph Shraibman > > > jks@selectacast.net > > > Increase signal to noise ratio. http://www.targabot.com > > > > -- Joseph Shraibman jks@selectacast.net Increase signal to noise ratio. http://www.targabot.com