[sheepdog] [PATCH 0/2] add cache options 'page' and 'unsafe'

[Liu Yuan]

On 10/22/2012 11:13 AM, MORITA Kazutaka wrote:
> This series introduces cache options 'page', which uses a page cache
> on storage nodes for vdi cache, and 'unsafe', which doesn't sync at
> all.
> 
> 'page' is useful when VMs are running on different cluster from sheeps
> and we can use a lot of memory on sheep nodes for a Sheepdog VDI
> cache.
> 
> 'unsafe' is useful when a datacenter can provide a reliable power and
> we are unlikely to lose in-memory data.  We can also use this option
> for testing purpose.

How can we assure that page cache won't be flushed to disk? I think we
can only do with autonomous pages via mmap(). Page cache will be flushed
back periodically by kernel.

> 
> 

I don't quite understand this unsafe mode. It looks the same to me as page.

I think your patch set is going to finer-control the fd flags for page
cache. So I think we can control it via disk cache, like disk:pagecache.

I am more concerned that the cache mode setting might look too
complicated to end users.

Thanks,
Yuan