As Kirk McKusick wrote ...
> Mounting on more than one system is generally problematical unless
> you are willing to have all systems read-only. The problem is cache
> coherence between the machines. If one changes a block, the other
> machines will not see it. Basically, this is why we have the NFS
> filesystem. That lets a disk be mounted on one machine, but shared
> out to others. If you wanted to write a protocol that would allow
> for multiple machines, then you would need to have some central
> coordinator running some sort of coherency protocol with a complexity
> akin to that of NFS.
I wonder how Tru64 is doing it. IIRC V5.0 Tru64 can do a cluster filesystem.
A CFS must have solved the coherency issue in some way.
Older revs had distributed raw devices (for Oracle and the like) but that
had all I/O go through one cluster member that did all the I/O for that DRD.
The I/O from the other cluster members was done via the Memory Channel to
the DRD-serving machine.
Interesting..
Wilko
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