[rc5] Sharing of buff files by multiple client processes

Stephen Langasek vorlon at dodds.net
Fri Jul 11 11:08:50 EDT 1997

On Fri, 11 Jul 1997, Guan Sin Ong wrote:

> On a multi-processor Unix system, where multiple rc5 processes will be
> run from the same binary and directory, only one buff-in and one
> buff-out are found, which means the processes are sharing the files. Is
> this sharing of buff files handled properly by rc5 program? Or what's
> the best way to run on a multi-processor system? (I am not talking about
> problem in a NFS, multi-platform environment.)

Not speaking from a position of authority, here, merely the authority that
comes from experience, but...

When you have multiple clients sharing the same files (whether they're on
different systems, or on different processors in the same system), each
client will grab a keyblock from the stack, work on it, and either 1)
finish the block and write to buff-out, 2) be forced to stop crunching and
put the half-finished block back on the pile in buff-in, or 3) crash and
die miserably, losing the data.  I remember something being said about
file locking coming into play, although I don't know the exact mechanism
for that, but until I see otherwise I'll assume the file locking is
sufficient to prevent corruption of data... :)

                               -Steve Langasek

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