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List:       linux-server
Subject:    Re: fallover for database server
From:       Ben Hoyt <ben () spectrumwireless ! net>
Date:       1999-01-30 4:33:58
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        You could do something along the lines of sharing the SCSI chain that
the drives are connected to - for the failover server, you would have to
set the card to read-only.  You could have the failover constantly check
(something as stupid as ping, or as complicated as issuing a network
query to the db) every 30 seconds, and if the remote fails, you can
spoof your MAC address on the failover server to be that of the
primary.  You would have to have your failover kill the primary, of
course.  Once the failover has taken over the service, you should have
it check more frequently (~15 seconds) for the primary service to come
back up - this may require a serial connection, or second set of network
cards, in order to do this, because of the MAC spoofing.  Once it sees a
connection, it could cease the MAC spoofing, and release the service to
the primary.


Mike Carpenter wrote:
>
> >Re Fallover for database servers
> >
> >We're becoming increasingly dependant on our database servers..
> >
> >It's not an issue of backup or replacement but maximum availability..
> >Even rebooting for maintenance of any kind takes out multiple systems
> >and is starting to feel unacceptable..
> >
> >I need a system that will allow me to take down and bring up
> >database servers.  Yes, current sessions will break; that's OK.  It's
> >also OK (for now at least) if the secondary servers are ReadOnly,
> >perhaps propagated from the master server (like Kerberos kprop)..
> >
> >Maybe the easiest thing to do would be to code it into the client
> >libraries.  Is there some way to do it with DNS or even hardware?
> >
> >Thanks
>
> Yes, it's available.  But it's not cheap. HP and Sun both have solutions,
> both using EMC mirrored drives.  Works really well.  I installed an HP
> solution for Motorola and, sure enough, when the primary system goes down
> the secondary takes over, data is completely intact. as you indicate the
> current connections are lost, but no data. And switchover is under 1 minute..
>
> BTW, we did this with HP-UX 11.0 and Oracle 8.04 and Informix 7.xx
>
> Contact sales at either Sun or HP (I'm sure others have similar solutions,
> too). They will be *very* happy to help you..
>
> OBlinux - I don't know of a real solution under linux
>
> Later....
> Mike

--
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Ben Hoyt       ben@spectrumwireless.net
Spectrum Wireless          907.272.1066
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