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Re: [Xen-users] Distributed xen or cluster?

To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Distributed xen or cluster?
From: "lists@xxxxxxxxxxxx" <lists@xxxxxxxxxxxx>
Date: Tue, 20 Jan 2009 10:25:08 -0600
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> Exactly what kind of redundancy are you looking for? Is it (for
> example) having several domUs serving the same web content and having
> a load balancer in front of them so traffic is balanced among working
> domUs?

Here's a small example.

I have a GFS cluster of servers which serve up LAMP services which uses two LVS 
(redundant) servers as a front end for load balancer. Each server has a fibre 
channel card to attach it to the FC network so that it can see the GFS volumes 
as it's own. It's a pretty nicely redundant service, if one server fails, 
nothing goes down, things just keep on running. The one problem I haven't 
bothered with is that if there is a failure, the user has to reconnect because 
the session gets messed up. Otherwise, it's fully redundant.

With my virtualization testing, things aren't so much fun. When a server goes 
down, or needs to be rebooted, or anything which causes it to have to be down, 
all guests on that server go down with it of course. Migrating over to another 
machine is pointless because it takes way too much work to migrate just to 
reboot a server.

Of course, what would be best would be proper redundancy, so that there are 
multiple containers working together as one. If one goes down, the others 
simply keep going and no servers go down.

I have no idea how I'll deal with win servers because they tend to need stupid 
re-activating when moved to different hardware, at least the limited experience 
I've had so far. Either way, that's not an issue because most of the servers, 
if not all, are going to be Linux.

I've not done anything with this yet because I'm fairly new to virtualization 
but even new, I have quickly realized that this is very badly needed. I've 
started with VMware Server 2.0, was about to migrate over ESX but decided it 
was time to try xen.

So, I'm looking for a way to have proper redundancy, not just migration because 
that's not an option when you just need to reboot or take a server down for 
some reason.

I'll post another question about storage separately so that this thread doesn't 
become too convoluted.

Mike


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