[sheepdog] [PATCH V2 4/4] collie: introduce '-o, --oid' option to 'collie vdi read' command

[Yunkai Zhang]

On Fri, Aug 24, 2012 at 12:57 AM, MORITA Kazutaka
<morita.kazutaka at lab.ntt.co.jp> wrote:
> At Fri, 24 Aug 2012 00:34:24 +0800,
> Yunkai Zhang wrote:
>>
>> On Thu, Aug 23, 2012 at 10:20 PM, MORITA Kazutaka
>> <morita.kazutaka at lab.ntt.co.jp> wrote:
>> > At Thu, 23 Aug 2012 21:46:55 +0800,
>> > Yunkai Zhang wrote:
>> >>
>> >> When inconsistency happens, in the worst case, we just need to make
>> >> replicas with the same value but needn't to care about which replica
>> >> is correct.
>> >>
>> >> But in the best case, only several objects were polluted, then this
>> >> patch can give us a chance to verify them, This patch is used to work
>> >> with 'collie vdi check' command, that is my original intention when
>> >> developed it.
>> >
>> > Well, replica inconsistency happens only when the VM terminates
>> > unexpectedly.  If the vm image needs a fix, the guest os filesystem
>> > should fix it.  What sheepdog should do is only keeping consistency so
>>
>> Can you explain how the guest os files system fix it?
>
> I meant fsck.

If correct one have been removed, how can fsck fix that? (I'm not
familiar with this command, I just have some doubts.)

>
> I don't fully understand yet what situation you want to avoid.  What
> kinds of problem happens to you if you fix consistency with wrong
> objects?

If fsck can help me to fix, I have no question, and this patch isn't
very important for me.

I just want to try our best to protect sheepdog's data integrity, I
haven't encountered any situation in real work, I didn't even
encountered VM's unexpected termination.

If fix consistency with wrong objects is really not harm, I do not
mind to drop this patch.


>
> Thanks,
>
> Kazutaka



-- 
Yunkai Zhang
Work at Taobao