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From: Georg Glas (glas_at_hollomey.com)
Date: Tue 08 Apr 2003 - 17:16:13 BST

Hi ...

i yust try to design, study and eveluate a solution to use vservers for high

Lets see some basic setup that we start from:

There are two machines (lets call them node A and node B) each running a bunch
of virtual servers with different services inside.

... some we can run active-active:
         (eg ldap, samba-ldap, cups, dns services, apache, dhcpd) ..
[despite the fact that some services might need fileservice syncronisation
using nfs, afs, coda or some other shared filesystem] (these services are
already working well in a vserver enviroment)

.. other service need to be run active-standby
        (eg http proxy server (yes indeed you can use some javascripting and hashing
to run it active-active, but most clients dont support this and require a
uniq ip addresse to be added) ftp server, socks server)
 when running in active-standby there must be a way to switchover the ip
address from one virtualserver on node A to a virtualserver on node B .. you
could do this by monitoring the servers with heartbeat and restarting the
complete server for adding/removing the iproot statment. This is a very slow
approch and would take some time (eg for a large squid cache filesystem this
could take up a minute or so).

So we have to start up the server and just switch the ip address using eg
vrrpd (http://www.off.net/~jme/vrrpd/index.html) running in the master-server
... however we cannot change the iproot statement any more in a running
virtual server, so there will be no way that services can bind to the new
added interface. So this solution want take us any further then here ..
(maybe someone could introduce a hack to change the iproot of a running

Another way would be using ip virtual server (some kernel hack) and direct
routing (http://www.linuxvirtualserver.org/VS-DRouting.html) but for the
standard ipvs design we would need a for block architecture (so two ipvs
redirectors, and two real servers) ... to make it ha, which is not what i
intend todo ..

so now my question did anyone solve this problem, and could point me to a
solution or is this yust some foolisch idea ?

Georg Glas
Hollomey Consultants GmbH
phone: +4331681139362   fax: +433168113934

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