[nSLUG] XEN & Heartbeat

Ian Campbell ian at slu.ms
Tue Jun 2 23:33:32 ADT 2009


On Tue, Jun 02, 2009 at 11:24:35PM -0300, Oliver Baltzer wrote:
> Ian Campbell wrote:
> > Assuming 1, Oliver's solution is probably the best, although it would
> > likely be that it would be more like restarting from a crash than a
> > cold boot. I expect you would need a fsck, probably mysql's table
> > check etc. because the VM's disk would have been left in a bad state.
> 
> Something to add here is that you would want the VM's disk images to be
> direct block devices, i.e. DRBD or DRBD/LVM, not images on a file
> system. I am not sure how Xen access disk images that are sitting on a
> file system, but the host OS may do some unwanted caching (likely making
> your VM really fast), which is another layer of non-persistent data that
> gets lost on a crash.

That would save your partitions, you might still have apps in a bad
state. MySQL is probably the only example on his list of that though.
I can't think of how a hot-cold setup would fare any better than if
you'd kill -9'd it.

A real DB might do better ;)



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