Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

[Andrew D. Ball]

It looks like I can do this by starting a domain from an SXP directly 
instead of a Python-based configuration.

If I use a suitable algorithm for generating UUIDs, I should be able to 
guarantee at least an extremely low probability of UUID collisions 
across an entire farm of systems running Xen.  I will read up some more 
on the ISO UUID algorithm commonly used by hardware manufacturers.  I 
don't trust it quite yet, but it does seem that this is in line with its 
purpose.

I'm not really fond of the behavior of domain name collisions.  I don't 
want to have to query some sort of farm-wide database to see if a domain 
name isn't being used to guarantee uniqueness, but I want to be able to 
guarantee that I'll never have a domain name collision when doing a live 
migration of a domU to another system.  They are nice to have around for 
being easily readable by humans though.

Thanks for your help.

Andrew

Anthony Liguori wrote:
> Andrew D. Ball wrote:
> 
>> Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to 
>> create a domU with a particular UUID?  I don't want the UUID for a 
>> domain to change when I destroy it and create it again from the same 
>> configuration.
> 
> 
> You could always make the domain's name it's UUID.
> 
> Regards,
> 
> Anthony Liguori
> 
>> This doesn't necessarily have to have anything to do with xenstore's 
>> being persistent, it could just involve a configuration option similar 
>> to the one for virtual NICs where MAC addresses can be assigned 
>> explicitly if desired but will be pseudo-randomly generated otherwise.
>>
>> Thanks for your help.
>>
>> Andrew
>>
>>
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@lists.xensource.com
>> http://lists.xensource.com/xen-users
>>
> 
> 

Re: Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

[Tim Freeman]

On Mon, 31 Oct 2005 18:12:52 -0500
"Andrew D. Ball" <aball@us.ibm.com> wrote:

> It looks like I can do this by starting a domain from an SXP directly 
> instead of a Python-based configuration.
> 
> If I use a suitable algorithm for generating UUIDs, I should be able to 
> guarantee at least an extremely low probability of UUID collisions 
> across an entire farm of systems running Xen.  I will read up some more 
> on the ISO UUID algorithm commonly used by hardware manufacturers.  I 
> don't trust it quite yet, but it does seem that this is in line with its 
> purpose.

I don't think Xen3 has changed, with UUIDs you'll run into this bug (for which I
have not yet submitted a patch for, I should do that). 

http://lists.xensource.com/archives/html/xen-devel/2005-07/msg00090.html

I was hastily adding support for UUIDs to the Globus workspace control program
and ran up against this problem because UUIDs can start with digits. Because I
couldn't wait to rely on a Xen patch, what I ended up doing for that was
stripping digits from the beginning of the UUID before sending it to Xen which
is clearly only a temporary hack. 

Tim 


> I'm not really fond of the behavior of domain name collisions.  I don't 
> want to have to query some sort of farm-wide database to see if a domain 
> name isn't being used to guarantee uniqueness, but I want to be able to 
> guarantee that I'll never have a domain name collision when doing a live 
> migration of a domU to another system.  They are nice to have around for 
> being easily readable by humans though.
> 
> Thanks for your help.
> 
> Andrew
> 
> Anthony Liguori wrote:
> > Andrew D. Ball wrote:
> > 
> >> Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to 
> >> create a domU with a particular UUID?  I don't want the UUID for a 
> >> domain to change when I destroy it and create it again from the same 
> >> configuration.
> > 
> > 
> > You could always make the domain's name it's UUID.
> > 
> > Regards,
> > 
> > Anthony Liguori
> > 
> >> This doesn't necessarily have to have anything to do with xenstore's 
> >> being persistent, it could just involve a configuration option similar 
> >> to the one for virtual NICs where MAC addresses can be assigned 
> >> explicitly if desired but will be pseudo-randomly generated otherwise.
> >>
> >> Thanks for your help.
> >>
> >> Andrew
> >>
> >>
> >>
> >> _______________________________________________
> >> Xen-users mailing list
> >> Xen-users@lists.xensource.com
> >> http://lists.xensource.com/xen-users
> >>
> > 
> > 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 

Re: Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

[Anthony Liguori]

Tim Freeman wrote:

>On Mon, 31 Oct 2005 18:12:52 -0500
>"Andrew D. Ball" <aball@us.ibm.com> wrote:
>
>  
>
>>It looks like I can do this by starting a domain from an SXP directly 
>>instead of a Python-based configuration.
>>
>>If I use a suitable algorithm for generating UUIDs, I should be able to 
>>guarantee at least an extremely low probability of UUID collisions 
>>across an entire farm of systems running Xen.  I will read up some more 
>>on the ISO UUID algorithm commonly used by hardware manufacturers.  I 
>>don't trust it quite yet, but it does seem that this is in line with its 
>>purpose.
>>    
>>
>
>I don't think Xen3 has changed, with UUIDs you'll run into this bug (for which I
>have not yet submitted a patch for, I should do that). 
>  
>
It's a feature, not a bug :-)

You can use either domid's or names with all commands.  For this to 
work, names cannot be integer.  The simple check is to prevent names 
from beginning with numbers (which is a common enough requirement on 
symbols).

FWIW, I'd recommend just prepending uuid- to the name instead of 
trimming the front off.

Regards,

Anthony Liguori

>http://lists.xensource.com/archives/html/xen-devel/2005-07/msg00090.html
>
>I was hastily adding support for UUIDs to the Globus workspace control program
>and ran up against this problem because UUIDs can start with digits. Because I
>couldn't wait to rely on a Xen patch, what I ended up doing for that was
>stripping digits from the beginning of the UUID before sending it to Xen which
>is clearly only a temporary hack. 
>
>Tim 
>
>
>  
>
>>I'm not really fond of the behavior of domain name collisions.  I don't 
>>want to have to query some sort of farm-wide database to see if a domain 
>>name isn't being used to guarantee uniqueness, but I want to be able to 
>>guarantee that I'll never have a domain name collision when doing a live 
>>migration of a domU to another system.  They are nice to have around for 
>>being easily readable by humans though.
>>
>>Thanks for your help.
>>
>>Andrew
>>
>>Anthony Liguori wrote:
>>    
>>
>>>Andrew D. Ball wrote:
>>>
>>>      
>>>
>>>>Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to 
>>>>create a domU with a particular UUID?  I don't want the UUID for a 
>>>>domain to change when I destroy it and create it again from the same 
>>>>configuration.
>>>>        
>>>>
>>>You could always make the domain's name it's UUID.
>>>
>>>Regards,
>>>
>>>Anthony Liguori
>>>
>>>      
>>>
>>>>This doesn't necessarily have to have anything to do with xenstore's 
>>>>being persistent, it could just involve a configuration option similar 
>>>>to the one for virtual NICs where MAC addresses can be assigned 
>>>>explicitly if desired but will be pseudo-randomly generated otherwise.
>>>>
>>>>Thanks for your help.
>>>>
>>>>Andrew
>>>>
>>>>
>>>>
>>>>_______________________________________________
>>>>Xen-users mailing list
>>>>Xen-users@lists.xensource.com
>>>>http://lists.xensource.com/xen-users
>>>>
>>>>        
>>>>
>>>      
>>>
>>
>>_______________________________________________
>>Xen-devel mailing list
>>Xen-devel@lists.xensource.com
>>http://lists.xensource.com/xen-devel
>>
>>    
>>
>
>  
>

Re: Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

[Tim Freeman]

On Mon, 31 Oct 2005 19:22:11 -0600
Anthony Liguori <aliguori@us.ibm.com> wrote:

> Tim Freeman wrote:
> 
> >On Mon, 31 Oct 2005 18:12:52 -0500
> >"Andrew D. Ball" <aball@us.ibm.com> wrote:
> >
> >  
> >
> >>It looks like I can do this by starting a domain from an SXP directly 
> >>instead of a Python-based configuration.
> >>
> >>If I use a suitable algorithm for generating UUIDs, I should be able to 
> >>guarantee at least an extremely low probability of UUID collisions 
> >>across an entire farm of systems running Xen.  I will read up some more 
> >>on the ISO UUID algorithm commonly used by hardware manufacturers.  I 
> >>don't trust it quite yet, but it does seem that this is in line with its 
> >>purpose.
> >>    
> >>
> >
> >I don't think Xen3 has changed, with UUIDs you'll run into this bug (for
> >which I have not yet submitted a patch for, I should do that). 
> >  
> >
> It's a feature, not a bug :-)
> 
> You can use either domid's or names with all commands.  For this to 
> work, names cannot be integer.  The simple check is to prevent names 
> from beginning with numbers (which is a common enough requirement on 
> symbols).

Sure ... but as we talked about in the thread I linked, it could check for all
numbers instead.  It's irrelevant to us now, but it did come as a surprise I
couldn't use something so useful as a straght uuid.

By the way, at the very least, the inclusion of "/" should be removed, it leads
to an error state.

> 
> FWIW, I'd recommend just prepending uuid- to the name instead of 
> trimming the front off.

That does sound like a better idea, thanks. 

Tim 


> 
> Regards,
> 
> Anthony Liguori
> 
> >http://lists.xensource.com/archives/html/xen-devel/2005-07/msg00090.html
> >
> >I was hastily adding support for UUIDs to the Globus workspace control
> >program and ran up against this problem because UUIDs can start with digits.
> >Because I couldn't wait to rely on a Xen patch, what I ended up doing for
> >that was stripping digits from the beginning of the UUID before sending it to
> >Xen which is clearly only a temporary hack. 
> >
> >Tim 
> >
> >
> >  
> >
> >>I'm not really fond of the behavior of domain name collisions.  I don't 
> >>want to have to query some sort of farm-wide database to see if a domain 
> >>name isn't being used to guarantee uniqueness, but I want to be able to 
> >>guarantee that I'll never have a domain name collision when doing a live 
> >>migration of a domU to another system.  They are nice to have around for 
> >>being easily readable by humans though.
> >>
> >>Thanks for your help.
> >>
> >>Andrew
> >>
> >>Anthony Liguori wrote:
> >>    
> >>
> >>>Andrew D. Ball wrote:
> >>>
> >>>      
> >>>
> >>>>Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to 
> >>>>create a domU with a particular UUID?  I don't want the UUID for a 
> >>>>domain to change when I destroy it and create it again from the same 
> >>>>configuration.
> >>>>        
> >>>>
> >>>You could always make the domain's name it's UUID.
> >>>
> >>>Regards,
> >>>
> >>>Anthony Liguori
> >>>
> >>>      
> >>>
> >>>>This doesn't necessarily have to have anything to do with xenstore's 
> >>>>being persistent, it could just involve a configuration option similar 
> >>>>to the one for virtual NICs where MAC addresses can be assigned 
> >>>>explicitly if desired but will be pseudo-randomly generated otherwise.
> >>>>
> >>>>Thanks for your help.
> >>>>
> >>>>Andrew
> >>>>
> >>>>
> >>>>
> >>>>_______________________________________________
> >>>>Xen-users mailing list
> >>>>Xen-users@lists.xensource.com
> >>>>http://lists.xensource.com/xen-users
> >>>>
> >>>>        
> >>>>
> >>>      
> >>>
> >>
> >>_______________________________________________
> >>Xen-devel mailing list
> >>Xen-devel@lists.xensource.com
> >>http://lists.xensource.com/xen-devel
> >>
> >>    
> >>
> >
> >  
> >
> 

Re: Re: [Xen-users] creating a domU with a particular UUID with xen-unstable

[Kip Macy]

[-- Attachment #1.1: Type: text/plain, Size: 2371 bytes --]

It would seem to me that if you either seeded the UUID from the initial
physical machine's MAC address (assuming that one can do that) or if you
concatenated a MAC address from the physical machine with a 64-bit time
value that your odds of collision would be vanishingly small.


-Kip

On 10/31/05, Andrew D. Ball <aball@us.ibm.com> wrote:
>
> It looks like I can do this by starting a domain from an SXP directly
> instead of a Python-based configuration.
>
> If I use a suitable algorithm for generating UUIDs, I should be able to
> guarantee at least an extremely low probability of UUID collisions
> across an entire farm of systems running Xen. I will read up some more
> on the ISO UUID algorithm commonly used by hardware manufacturers. I
> don't trust it quite yet, but it does seem that this is in line with its
> purpose.
>
> I'm not really fond of the behavior of domain name collisions. I don't
> want to have to query some sort of farm-wide database to see if a domain
> name isn't being used to guarantee uniqueness, but I want to be able to
> guarantee that I'll never have a domain name collision when doing a live
> migration of a domU to another system. They are nice to have around for
> being easily readable by humans though.
>
> Thanks for your help.
>
> Andrew
>
> Anthony Liguori wrote:
> > Andrew D. Ball wrote:
> >
> >> Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to
> >> create a domU with a particular UUID? I don't want the UUID for a
> >> domain to change when I destroy it and create it again from the same
> >> configuration.
> >
> >
> > You could always make the domain's name it's UUID.
> >
> > Regards,
> >
> > Anthony Liguori
> >
> >> This doesn't necessarily have to have anything to do with xenstore's
> >> being persistent, it could just involve a configuration option similar
> >> to the one for virtual NICs where MAC addresses can be assigned
> >> explicitly if desired but will be pseudo-randomly generated otherwise.
> >>
> >> Thanks for your help.
> >>
> >> Andrew
> >>
> >>
> >>
> >> _______________________________________________
> >> Xen-users mailing list
> >> Xen-users@lists.xensource.com
> >> http://lists.xensource.com/xen-users
> >>
> >
> >
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

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