[sheepdog] [PATCH] sheep: add simple_store driver again

[Liu Yuan]

On 08/24/2012 03:28 PM, Liu Yuan wrote:
>>> >>
>>> >> I'll go to update the farm's io path to use defaul_xxx functions, I
>>> >> think this simple store implementation can be nicely applied to farm.
>> > 
>> > The update will change the data layout of farm.  How about introducing
>> > 'farm2'?  I guess farm and farm2 can share all files other than
>> > farm.c.
> No, this won't change the data layout of farm at all. Just adding
> another .stale file directory, which is useless after cluster becomes
> stable. With .stale, old .farm directory will be solely used for storing
> snapshot objects, which is also relevant to ordinary data objects in
> working directory.

This just changes internal recovery handling of farm, it is why I
suggested to merge simple store idea into farm. With this new idea, the
farm recovery + object handling in working directory will be the same as
your simple store, plus data de-duplication feature for sha1 objects. So
cluster snapshot object will be currently the only user of sha1 object,
but I think we can store more objects as sha1 object to take advantage
of data de-duplication in the future.

Thanks,
Yuan