Re: [Xen-devel] [Notes for xen summit 2018 design session] Process changes: is the 6 monthly release Cadence too short, Security Process, ...

[George Dunlap <George.Dunlap@xxxxxxxxxx>]

> On Jul 5, 2018, at 5:23 PM, Ian Jackson <ian.jackson@xxxxxxxxxx> wrote:
> 
> Sander Eikelenboom writes ("Re: [Xen-devel] [Notes for xen summit 2018 design 
> session] Process changes: is the 6 monthly release Cadence too short, 
> Security Process, ..."):
>> Thursday, July 5, 2018, 5:14:39 PM, you wrote:
>>> So that means that often, and at least from one test flight to the
>>> next, all of the base dom0 OS needs to be copied from somewhere else
>>> to the test host.  This is not currently as fast as it could be, but
>>> running d-i is not massively slower than something like FAI.
>> 
>> how about using (LVM) snapshotting (whch does COW) and drop the
>> snapshots after a test ?  Only do a new OS install once a day/week
>> (or point releas) and only after having an OSSTEST pass ?  That
>> should have fairly little overhead.
> 
> I'm sorry to have to say this, but you seem not to have read what I
> wrote above.
> 
> Leaving aside other questions about using LVM for a whole machine
> including possible EFI system partition, bootloader etc., where would
> the base image be for this LVM snapshot ?
> 
> If it is on the host itself then the previous test can corrupt it.
> This is not theoretical: we are doing OS and hypervisor development.
> Breakage is to be expected.

What would you think of a “backup partition” scheme instead?  I.e., make (say) 
/dev/sda1 and /dev/sda2  identical size, install to /dev/sda1, use a small 
“snapshot” netboot utility to dd it into /dev/sda2.  Run a test, then dd from 
/dev/sda2 back into /dev/sda1.  If this were only a few gigs it shouldn’t take 
more than a minute or two.  How long does a full install take?

In theory of course a wild OS write could corrupt something in an unmounted 
partition, but in practice the chance of that happening in *our* testing seems 
seems pretty tiny.  (Embedded device manufacturers seem to think this is rare 
enough to update firmware with, and they have a lot more to lose than we do.)

 -George
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