Messages in this thread | | | Date | Fri, 25 Oct 1996 19:19:15 +0100 | From | Dieter Kaeppel <> | Subject | Re: Memory upgrade: not faster / nfs |
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Christoph Trautwein wrote: > > Problem: > ! NFS is a filesystem. Filesystems are not cached. > ! The only thing that's cached in UN*X are block > ! devices. This is the wrong place to cache. [...] > Questions: > Is it correct how I see these things? > Why are filesystems not buffered? > Is there a nfs implementation that does buffering?
They are not buffered due to a lack of protocols which recognices changes in the remote filesystem. A protocol which transfers all changes in files may slow down the system dramatically, if
- the client is not as fast as the server - the connection is very slow - many clients using a server, all changes then must be transfered vise versa
Furthermore this would cause a load on the client even it is not used.
My suggestions to solve this really nasty problem are the following:
- only on one client used filesystems (not used by the server) could be cached (rarely used) - caching of read only filesystems is possible (splitting into read only part eg. /usr/* and a read-write part) - introduce an cache protocol, working this way:
- whenever the client opens a file for reading, first there is searched in the clients cache - if found, the file dates are compared over network - if equal use the clients cache - if not transfer from server - if not, transfer from server
- whenever the client opens a new file for writing, transfer while closing - whenever a file on the server is opened for appending or read-write go the same way as opening for reading, transfer it back while closing
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