Jail hot migration
freebsd at deman.com
Fri Sep 10 15:17:15 UTC 2010
There are other issues too - like network I/O, particularly dealing with established TCP connections? Basically, you have to retain the in-state 'memory' of the machine being migrated from, while also letting all those 3rd party sockets know that everything is okay
Thus far, I have yet to see any vendor that delivers 'zero downtime' virtual migrations. There is always downtime - question is whether it is costed in terms of milliseconds, seconds, minutes, hours, or worse?
Definitely worth doing though. Personally, I have found value in running OSPF/BGP on the jail host itself, and putting the actual jails on the loopback interface. It certainly does not solve the problem in terms of 'minute' by any means, but having the Iayer-3 component work automatically definitely helps.
I think this idea is a worthwhile goal, but I would much, much rather see NFSv4 and ZFS wrapped up first.
On Sep 9, 2010, at 9:28 PM, Peter Toth wrote:
> Hi guys,
> I was lately thinking around jail hot-migration feature where one jail
> could be moved from one host to another without
> shutting it down, something like vmotion in VMware world.
> The storage layer should be easy with zfs send and receive or some form
> of shared storage. The tricky part would
> be a memory copy from one node to another and also the CPU handling.
> Anyone has an idea how this could be achieved? I guess it would require
> a kernel module which could take care of memory
> reservations and a daemon to copy and incrementally sync the jails
> memory across.
> Then also there is the CPU problem..
> Sounds like a fair amount of work and development.
> All comments are welcomed!
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