VMware and HA solutions

Marco Wiese mwiese at beit.de
Mon Mar 10 12:10:20 MET 2008


Hi,

you're right, if your ESX hardware gets in trouble and dies, the guest 
systems are transferred to the remaining hosts. But you have definitely a 
downtime, because in any case, HA will shutdown/power down the VM guests. 
Just have a try (if you have an ESX test-system) and remove the ethernet 
cable of the console interface. Your guests will be halted, if you don't 
have configred anything else (default). The other alternative, ESX hosts 
dies, is just the same. The hosts has no time to move the guest systems, 
because the host is already down and unable to act.

In fact: If you talk about HA, you talk about a minimum of downtime! No 
matter if the ESX hosts is alive but isolated or ESX host freezes/dies. 
You can't avoid the possibility of a host failure - ESX or not. A real 
hardware can also get into trouble - so what. Thats the risk of IT! :-))

But with HA, you have the advantage of "high availability". Where other 
"real" hardware systems are still down (for long time), your virtual 
machine is already up and running within some minutes after hardware 
failure!

Regards
Marco

"Euler, Christian" <euler at aov.de> schrieb am 10.03.2008 11:18:53:

> Hi,
> 
> AFAIK the VMWare HA tools provide high availability at operating 
> system level. So if your hardware fails, you're fine because your guest 
system
> will be transferred to another host. But if your application crashes
> (SAP in this case), you'll need a HA software that runs inside your 
> guest system
> and handles such situation by failing over to a standby node (which 
> can be another VMWare guest system).
> 
> A good idea would be a combination of the two:
> 
> - VMWare HA for hardware failures (move the entire guest system to 
> another host)
> - a HA cluster software (linux-ha for example) to handle application
> failures (switch to a standby node)
> 
> Maybe there's a SAP Note which has more information on how to set up
> a clustered system..
> 
> Regards,
> Christian Euler
> 
> AOV IT.Services GmbH
> Bartholomäusweg 32
> 33334 Gütersloh
> Tel. +49 (5241) 9463-101
> Fax +49 (5241) 9463-55
> eMail euler at aov.de
> http://www.aov.de
> 
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> 
> 
> "With sufficient thrust, pigs fly just fine. However, this is not 
> necessarily a good idea. It is hard to be sure where they are going 
> to land, and it could be dangerous sitting under them as they fly 
> overhead." (RFC 1925)
> 
> 
> > -----Original Message-----
> > From: linux.general-bounces at listserv.sap.com 
> > [mailto:linux.general-bounces at listserv.sap.com] On Behalf Of 
> > Michele Donna
> > Sent: Monday, March 10, 2008 10:35 AM
> > To: linux.general at listserv.sap.com
> > Subject: RE: VMware and HA solutions
> > 
> > Hi,
> > 
> > What I'm trying to understand is if we can manage SAP
> > instances simply using VMware HA tools or if we have to use
> > another layer of ha software just for SAP.
> > 
> > If VMware HA can provide a sort of Business continuity
> > solution that's fine for us.. 
> > 
> > 
> > thanks and regards,
> > Michele
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> linux.general at listserv.sap.com
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