earlier i said rpc and cache coherence are duals

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Unformatted text preview: allbacks. ***We mentioned that NFS allows for transparent recovery when server or clients fail, using idempotent operations and TTL based coherence. Can we get transparent recovery with callbacks? (Recover by asking others what server state was.) ****Why use write back coherence vs. just write through? (If data is written repeatedly.) ***Why not always use write back coherence? In the presence of failures, would be a blocking protocol, unless you log writes to (multiple disks) to allow remote recovery. Some examples of cache coherence in practice. Ivy: Illusion of shared-­‐memory, using virtual memory paging hardware. Page table marked as invalid, read-­‐only, read-­‐write (owned). Take page fault to transition between states. Why is Ivy cool? All the advantages of *very* expensive parallel hardware. On cheap network of workstations. No h/w modifications required! Do we want a single cache coherent address space? Or perhaps we just want programmer/compiler to issue remote references to remote data, where programmer should manage bringing the data b...
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