Re: [Xen-devel][PATCH]: Support dynamic resizing of vbds

["Ky Srinivasan" <ksrinivasan@xxxxxxxxxx>]

>>> On 3/11/2010 at  6:13 PM, in message <4B997922.1080407@xxxxxxxx>, Jeremy
Fitzhardinge <jeremy@xxxxxxxx> wrote: 
> On 03/11/2010 02:01 PM, Ky Srinivasan wrote:
>>
>>    
>>>>> On 3/11/2010 at  4:44 PM, in message<4B996436.1000600@xxxxxxxx>, Jeremy
>>>>>          
>> Fitzhardinge<jeremy@xxxxxxxx>  wrote:
>>    
>>> On 03/11/2010 12:15 PM, Pasi KÃrkkÃinen wrote:
>>>      
>>>> On Tue, Mar 09, 2010 at 01:39:23PM -0700, Ky Srinivasan wrote:
>>>>
>>>>        
>>>>>
>>>>>          
>>>>>>>> On 3/9/2010 at  3:35 PM, in 
>>>>>>>> message<20100309203557.GJ1878@xxxxxxxxxxx>, Pasi
>>>>>>>>
>>>>>>>>                
>>>>> KÃrkkÃinen<pasik@xxxxxx>   wrote:
>>>>>
>>>>>          
>>>>>> On Tue, Mar 09, 2010 at 01:31:17PM -0700, Ky Srinivasan wrote:
>>>>>>
>>>>>>            
>>>>>>>
>>>>>>>              
>>>>>>>>>> On 3/9/2010 at  3:15 PM, in 
>>>>>>>>>> message<20100309201529.GH1878@xxxxxxxxxxx>, Pasi
>>>>>>>>>>
>>>>>>>>>>                    
>>>>>>> KÃrkkÃinen<pasik@xxxxxx>   wrote:
>>>>>>>
>>>>>>>              
>>>>>>>> On Tue, Mar 09, 2010 at 12:56:11PM -0700, Ky Srinivasan wrote:
>>>>>>>>
>>>>>>>>                
>>>>>>>>> The attached patch supports dynamic resizing of vbds.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                  
>>>>>>>> Nice! Did you also implement the xm/xend side of resizing?
>>>>>>>>
>>>>>>>>                
>>>>>>> My goal was to not have the end-user do anything other than what
>>>>>>> was minimally required to  resizing the device on the host side.
>>>>>>> Once the device is resized on the host side, this capacity change
>>>>>>> is propagated to the guest without having to invoke any xm command.
>>>>>>>
>>>>>>>
>>>>>>>              
>>>>>> Oh, even better!
>>>>>> What version of the kernel did you test with? 2.6.27?
>>>>>>
>>>>>>            
>>>>> I tested this on 2.6.32. The patches should apply to earlier kernels 
>>>>> without
>>>>>          
>>> too much trouble.
>>>      
>>>>>
>>>>>          
>>>> Great!
>>>>
>>>> Jeremy: Hopefully you can add this patch to your tree.
>>>>
>>>>        
>>> It applied fairly cleanly, but I haven't tested it yet.  Ky, by 2.6.32 I
>>> assume I mean your one, not pvops? (Because your patch is touching
>>> blkfront in the wrong place.)
>>>      
>> Yes. This patch was against our sles11 sp1.
>>    
> 
> What happens if the frontend doesn't support the resize, and the device 
> shrinks?  Will the backend just raise IO errors for out of range requests?

Clearly, resizing is an operation that ought to be done with great care and 
co-ordination between the administrators of the guest and the host. If the 
device on the host side is shrunk without co-ordinating with the guest,  seeing 
I/O errors will be the least of our problems!  
The situation you describe can occur today without this patch - consider the 
case where an LVM based device is resized on the host side (device is shrunk as 
in your example). We will be generating I/O errors for out of range request on 
the backend in this scenario. Assuming all the co-ordination is done, this 
patch automates propagating the capacity change without having to detach and 
attach the storage from the guest.

Regards,

K. Y 
> 
>      J
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel