[sheepdog] [PATCH 0/2] add cache options 'page' and 'unsafe'
namei.unix at gmail.com
Mon Oct 22 07:08:08 CEST 2012
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
> '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
> '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.
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