[sheepdog] [PATCH v0, RFC] sheep: writeback cache semantics in backend store

[MORITA Kazutaka]

At Mon, 20 Aug 2012 13:51:08 +0800,
Liu Yuan wrote:
> 
> I am suspicious that this approach is really useful:
> 
>  1. suppose we can only call sync() to flush page cache on each node.
> With a cluster that runs hundred of images, the sync() request will be
> issued almost every second, this kind of request storm will put this
> idea to useless, compared to SYNC open flag.
>  2 even if we are working with syncfs(), the benefit will be offset by
> the complexity to find all the location of specified VDI and send
> requests one by one

I guess this approach will give benefit only when the numbers of nodes
and VMs are small, but it's okay if it's not turned on by default.
Anyway, I'd like to see more benchmark results (e.g. running dbench on
several VMs simultaneously) before accepting this patch.

Thanks,

Kazutaka