Re: [Xen-devel] [PATCH] xend: drbd improvements

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

According to the block-drbd script's comments, live migration with
DRBD based disks
require dual primary setup and the block-drbd script automatically handles
 "changing the target host's vm disk to primary" when live migration
is initiated.

Removing drbd support from xend would necessitate an external agent to
actually promote the guest disk in target host to primary mode.

shriram


On Thu, Dec 16, 2010 at 4:45 PM, Jim Fehlig <jfehlig@xxxxxxxxxx> wrote:
> Jim Fehlig wrote:
>> Jim Fehlig wrote:
>>
>>> Ian Jackson wrote:
>>>
>>>
>>>> Jim Fehlig writes ("[Xen-devel] [PATCH] xend: drbd improvements"):
>>>>
>>>>
>>>>
>>>>> xend: drbd improvements
>>>>>
>>>>> 1) drbdadm state is debrecated, and the script tries to detect the
>>>>> primary/secondary information from the deprecated message
>>>>> 2) os.popen2 does not work with the array as argument
>>>>> 3) popen2 is deprecated since python2.6
>>>>>
>>>>>
>>>>>
>>>> Forgive my ignorance, but: why does xend need to mess with drbd at
>>>> all ?  Why can't it just open the block device ?
>>>>
>>>>
>>>>
>>> Good question.  I too was surprised to see special casing of drbd within
>>> xend.  Seems c/s 20158 added this code to allow bootloaders (pygrub,
>>> domUloader, et. al.) to work with drbd devices using the 'drbd:resource'
>>> syntax.  Perhaps the author of that patch (cc'd) can provide more
>>> details.
>>>
>>
>> The patch author's mail address is no longer valid, so we won't be
>> receiving any feedback from him :-(.
>>
>
> Sorry for the delay here, but I finally got around to investigating this
> further.  As it turns out, drbd's block-drbd script handles all of the
> details that c/s 20158 introduces within xend :-(.  IMO, this c/s should
> be reverted as it causes a regression.  I've tested drbd without this
> changeset and it works fine.
>
> Regards,
> Jim
>
>
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>



-- 
perception is but an offspring of its own self

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