On Fri, 2010-08-13 at 17:09 +0300, Dan Frincu wrote:
>
> > > Absolutely, RHCS != IPVS ... I do got that, sorry for my mis-stating it
> > > as such.
> > >
> > > My response and focus should not have been squarely on IP takeover and/or
> > > load-balancing -- as I was not even thinking (strangely) that CMAN was
> > > even part of Ana's question (how the {bleep} did I come to that?) It
> > > could very well be in play, and that it might be an issue considering its
> > > LAN requirements. My bad comes from our tendancies to only implement
> > > RHCS for IPVS only; and all that it offers in cman, fencing, clvmd,
> > > rgmanager, et al is only configured & started when we have GFS / GFS2
> > > filesystems in play.
> > >
> > > Slightly OT, I have "heard" that multicasting can be routed -- is that
> > > true, and if so, couldn't cman then work on different subnets? Or is
> > > there some other constriction or no-no besides "best practices" that I am
> > > missing? And I know you cannot have a node playing in two clusters,
> > > despite configuring it to meet network requirements, which could be
> > > construed as a shame.
> > >
> > >
> > CMAN relies on multicast that can be routed indeed, but the services IP
> > address (in the HA world) are in general unicast IP addresses. How would
> > you manage these IP failover if on different subnets ?
> >
> When a company owns an AS number and a Provider Independent subnet, it
> is possible to announce via BGP that subnet via 2 separate
> geographical sites, while running a separate subnet for each site; the
> active site would announce it normally and the backup/failover site
> would announce it by prepending it's own AS number to the AS_PATH
> attribute. Therefore, if the main site fails, IP traffic would go to
> the only remaining option, the backup/failover site. But this is more
> related to IP routing then anything else.
> My 2c.
As you're saying it's IP routing related.
On the failover site (the one with the longest AS_PATH) you have means
to reach that subnet (the one you advertise to the outside) either by a
directly connected interface or by internal routes to that subnet.
> > > Ok, have a good night! Myself, I am off to the first tee ... :)
> > >
> > >
> > > -----Original Message-----
> > > From: [email protected]
> > > [mailto:[email protected]] On Behalf Of Laszlo Beres
> > > Sent: Thursday, August 12, 2010 3:06 PM
> > > To: linux clustering
> > > Subject: Re: [Linux-cluster] RHCS separate datacenter
> > >
> > > On Thu, Aug 12, 2010 at 8:35 PM, <[email protected]> wrote:
> > >
> > >
> > > > stretches a 100 inches or a 100 miles. I think Ana should reveal more
> > > > about her implementation rather than hearing about yours. ;)
> > > >
> > > Cannot agree more :)
> > >
> > >
> > > > And what part of what I said is "false"? I didn't say anything that
> > > > fail-over AND load-balancing were required. Fail-over can be achieved
> > > > in numerous ways and without RH supplied tools; the load-balancing is
> > > > native to Linux using IPVS. But back to the original question: will
> > > > Red Hat support ... ? If you use your OWN fail-over strategy, you OWN
> > > > it.
> > > >
> > > It was your statement "RHCS is IPVS" that I felt false.
> > >
> > >
> > > > Yes, OpenAIS (and likewise the former pulse on RHEL4, sorry for dating
> > > > myself) is for fail-over which (either) can operate on different LANs.
> > > > And to my knowledge and not practical use, the load-balancing (IPVS)
> > > > can work on different LANs -- if the tunneling option is used. But my
> > > > point was that I have not seen any implementation that also maintains
> > > > IPVS client-session tracking on DIFFERENT LANs (which is NOT a problem
> > > > if it is on the same physical LAN, like your setup). It is that last
> > > > point that has obvious implications on the scope and objectives for
> > > > those seeking a "supportable" Linux-based solution.
> > > >
> > > I'm afraid there's still a misunderstanding there - either on my or your
> > > side.
> > >
> > > Pulse was and is a mechanism to ensure a heartbeat channel between two
> > > ipvs primary and backup routers. Pulse never had anything to do in the
> > > failover cluster core (which is cman in RHEL4, or OpenAIS starting with
> > > RHEL5). cman is not supported to be operated on different subnets.
> > >
> > >
> > > > Have a great day!
> > > >
> > > Rather night here in Europe ;)
> > >
> > > --
> > > László Béres Unix system engineer
> > > http://www.google.com/profiles/beres.laszlo
> > >
> > > --
> > > Linux-cluster mailing list
> > > [email protected]
> > > https://www.redhat.com/mailman/listinfo/linux-cluster
> > >
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> > >
> >
> >
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>
> --
> Dan FRINCU
> Systems Engineer
> CCNA, RHCE
> Streamwide Romania
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> Linux-cluster mailing list
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