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Re: [Xen-devel] highly available xen

On Thu, Feb 17, 2005 at 09:04:25PM +1100, James Harper wrote:
> Has anyone done any work in developing some heartbeat scripts (or any
> other method) for making  xen domains highly available across multiple
> physical machines?

Yes, but basic work, for a course.

> By my reckoning the hurdles to overcome are:
> . make absolutely sure that the same domain doesn't start twice and hose
> it's filesystem (I've done this. It isn't pretty)
1. xm list | grep domain
2. filesystem shared by drbd, only one can mount it

> . migrate a domain in the case of an orderly shutdown
1. xm save
2. xm load

> . restart a domain on another physical server in the case of a complete
> xen crash
1. standard heartbeat script and configuration  (xen::intsrv xen::www ...)

> . add some smarts to know how many domains a physical server can support
> . prioritise critical domains over non-critical domains (eg a primary
> mail server might take priority over a secondary dns server)

Not at the moment. The heartbeat configuration starts the priority
servers first, but a failure starting one causes heartbeat to fail the
takeover process.

> Any thoughts?
On my agenda:
1. export devices (ex, via gnbd)
2. leave heartbeat. create a monitoring daemon on each member with
support for dynamic migration and startup due to load on the machines.

Luciano Rocha

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