Locality and caching in parallel/distributed file systems

[Andrew Fant]

Morning all,
	Lately, I have been thinking a lot about parallel filesystems in
the most un-rigourous way possible.  Knowing that PVFS simply stripes the
data across the participating filesystems, I was wondering if anyone had
tried to apply caching technology and file migration capacities to a
parallel/distributed filesytem in a manner analagous to SGI's ccNuma
memory architecture.  That is, distributing files in the FS to various
nodes, keeping track of where the accesses are coming from, and moving
the file to another node if that is where some suitable percentage of the
reads and/or writes are coming from.  Also, potentially allowing blocks
from local files to be cached in disk on a local node until a write to
those blocks elsewhere invalidates the cache (I know the semantics for
this theoretically are in NFS, but NFS doesn't scale, and is dead 8-).
	I admit that I am not a computer science graduate, nor a
semi-professional developer, so I have no idea if this has been or could
be done, but it keeps rattling around in my head as an idea, and I would
appreciate any feedback that people can give.  Please forgive my ignorance
if I turn out to have reinvented the edsel.

Andy

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