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[Xen-users] Re: [Xen-devel] (strange idea) unfriendly migration

To: George Shuklin <george.shuklin@xxxxxxxxx>
Subject: [Xen-users] Re: [Xen-devel] (strange idea) unfriendly migration
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Mon, 1 Nov 2010 10:15:18 +0000
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At 20:07 +0100 on 29 Oct (1288382841), George Shuklin wrote:
> Good day.
> As we all know, xen requires assist from VM to migrate it. If VM will
> acts wrong during migration, it will crash, or behave strangely until
> reboot (nice sample - default -xen kernel in lenny).
> We need to accept changes in domU during migration: other domain id,
> new vbd/vif and so on.
> This fine until we talks about friendly VM. But if VM is not very
> friendly? For example, VM's user can upgrade kernel to different -xen,
> which one working fine with normal mode, but incompatible with
> migration? (Pretty typical situation for any kind of cloud environment
> or hosting).

The user can break their VM's kernel in all sorts of other ways too. :)

> If we create HVM-based overlay for PV-guest to keep thing unchanged, we
> can make migration much simpler.

Nice idea.  I'm not sure it's better than just using HVM for the guest
in the first place, though - that way the user can install pretty much
any kernel they want.  And the performance would be worse than either
plain PV or plain HVM.



Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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