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From: jhh+@ANDREW.CMU.EDU (John Howard)
Newsgroups: comp.soft-sys.andrew
Subject: Re: Andrew file cache
Message-ID: <0bma_XS00Vs200gExR@andrew.cmu.edu>
Date: 26 Feb 91 13:29:07 GMT
References: <2448@njitgw.njit.edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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Bruce,

First, the Andrew File System does not support diskless workstations
directly.  It should possible to use AFS in conjunction with something
else which supported diskless workstations, but AFS assumes a private
disk for caching.

When the AFS server starts up, it regards cached files to be suspect in
the sense that it checks with the server before using one.  If the
server gives back the same timestamp as the file has, the cache manager
proceeds to use the cached copy; otherwise it discards it and fetches a
current copy from the server.  In either case, the server remembers that
the client is interested in the file.  If later the file changes, the
server uses a "call-back" to notify all interested clients.  Upon
receiving a call-back notification, the client again starts regarding
the file as suspect.  This means that the server can invoke call-back
notifications whenever it wants to - the only harm done is that the
client will re-validate the file the next time it uses it.

Hope this helps.

John Howard


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