Re: ETCP Project

["Jeff Darcy" <jeff@tambreet.com>]

> > It's still dangerous, because you don't have anything forcing one
> > node to be passive, just convention and wishful thinking.  That is,
> > the 'mirror' FS is mounted and active on the second machine.  There's
> > nothing to keep it from writing.
>
> What makes you think that? Yes, this is a concern, but there are
> technical ways to ensure that. The underlying FS can sit on a path
> that the user-level daemon opens and then chmods one of the elements
> to something such that no one else can go there.

I don't think that will work.  A lot of metadata blocks are shared across
files with no other relationship.  If you're working on file A, that may
involve metadata blocks X, Y, and Z.  The only way you can be *sure* nobody
else is using X, Y, or Z would be to block out access to the entire
filesystem...unless, that is, you know an awful lot about the metadata
structure, and that's exactly what I thought you were trying to avoid.


Linux-cluster: generic cluster infrastructure for Linux
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