Stateful when nfs first introduced failure was a

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Unformatted text preview: ts of client-server interaction and excess communications Some of this is due to stateless nature and conservative consistency consistency mechanisms What What is new? Stateful (when NFS first introduced, failure was a bigger issue) consequences? open on remote files per client caching state -> integrate all the NFS protocols into one (i.e locking) Uses TCP More security – work with windows ACLs *Compound RPC – combine several RPCs together *Delegation for files - client cache consistency *Lease-based locking Compound Compound RPC Goal is to reduce traffic – chain requests together Complex calling interface lookup gets inode getattr Locking Locking Lease based locks Server defines a lease for per client lock state client has lock for K time units; automatic expiration; can be renewed Open sets lock state, including lock owner (clientid, pid) Delegation Delegation Intent is to reduce traffic: expiring cache blocks, fetching time-stamps For single owner files … this is wasted overhead Server decides to hand out a “delegation” at open aggressive caching (avoid server contact), cache lock state If client accepts, client provides callback Server will re-claim a delegation if file is opened by another client Many read delegations, or one write delegation Scenarios Scenarios that favor Delegation Provenance Provenance Next Next time Parallel and Distributed Systems OS Design Final MOS Chapters 8, 13...
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