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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 mechanisms What
What is new?
Stateful (when NFS first introduced, failure was a bigger issue)
open on remote files
per client caching
state -> integrate all the NFS protocols into one (i.e locking)
More security – work with windows ACLs
*Compound RPC – combine several RPCs together
*Delegation for files - client cache consistency
*Lease-based locking Compound
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
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
Parallel and Distributed Systems
MOS Chapters 8, 13...
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This document was uploaded on 04/02/2014.
- Summer '14
- Operating Systems