[sheepdog] [PATCH V4 2/2] collie: optimize 'collie vdi check' command

[MORITA Kazutaka]

At Mon, 3 Sep 2012 23:18:11 +0800,
Yunkai Zhang wrote:
> 
> 
> 
> 发自我的 iPhone
> 
> 在 2012-9-3，22:44，MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp> 写道：
> 
> > At Mon, 3 Sep 2012 22:14:56 +0800,
> > Yunkai Zhang wrote:
> >> 
> >> If 'collie vdi check' must read valid objects, what does it check?
> > 
> > It fixes vdi inconsistency after gateway (and qemu) failure.  It looks
> > completely wrong for clients to see data inconsistency in other
> > scenarios.
> 
> How can we know wether a cluster is consistent?
> 
> Can we promise sheepdog's code is always correct, will not cause data inconsistency except for gateway failure?
> 
> After we found inconsistency, showing the difference to user instead of repairing it directly, can give us a chance to check if program's bug or just gateway failure, doesn't it?

Please give me a concrete example.

When 'collie vdi check' shows that some sha1 values are A and the
others are B, how can you determine whether it is caused by a
program's bug or just gateway failure?  Just showing "there is data
inconsistency in object xxxx" isn't enough?

Thanks,

Kazutaka