Callbacks, instead of assuming your data is good for some short period
of time.  It's all well and good that there are mechanisms to know that
data has changed, but without some leasing/callback/(ugh)mandatory
locking, you're just estimating consistency.

  -Dan 

-----Original Message-----
From: David Howells [mailto:dhowells@redhat.com] 
Sent: Friday, December 19, 2008 5:20 PM
To: Bryan Henderson
Cc: dhowells@redhat.com; Andrew Morton; Muntz, Daniel;
linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org;
nfsv4@linux-nfs.org; rwheeler@redhat.com; sfr@canb.auug.org.au;
steved@redhat.com
Subject: Re: Pull request for FS-Cache, including NFS patches

Bryan Henderson <hbryan@us.ibm.com> wrote:

quoted text
> > > AFS was designed to support local disk cache, so with callbacks 
> > > you can get a consistent system.
> > 
> > It's less the callbacks and more the data version number that's
important.
quoted text
> 
> Maybe for consistency, but for the performance benefits of local disk 
> caching, I believe the callbacks are pretty important.

Indeed, but he said "so with callbacks you can get a _consistent_
system".

David
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