parker@vienna.njit.edu (Bruce Parker) (02/26/91)
Does Andrew retain or discard disk cache entries across reboots? The description by Satyanarayanan in Mullender's Distributed Computing, page 163, says they are retained, however, on page 166, he writes that ``When a workstation is rebooted, Venus considers all cached files and directories suspect.'' Is he considering diskless stations in the second case? Cheers, -- Bruce Parker 4314 Infotech (201) 596-3369 Computer and Information Science Department parker@vienna.njit.edu New Jersey Institute of Technology, Newark, New Jersey 07102 USA
jhh+@ANDREW.CMU.EDU (John Howard) (02/26/91)
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