Re: [Ocfs2-devel] [RFC] nodemanager, ocfs2, dlm

[Lars Marowsky-Bree <lmb@suse.de>]

On 2005-07-20T11:35:46, David Teigland <teigland@redhat.com> wrote:

> > Also, eventually we obviously need to have state for the nodes - up/down
> > et cetera. I think the node manager also ought to track this.
> We don't have a need for that information yet; I'm hoping we won't ever
> need it in the kernel, but we'll see.

Hm, I'm thinking a service might have a good reason to want to know the
possible list of nodes as opposed to the currently active membership;
though the DLM as the service in question right now does not appear to
need such.

But, see below.

> There are at least two ways to handle this:
> 
> 1. Pass cluster events and data into the kernel (this sounds like what
> you're talking about above), notify the effected kernel components, each
> kernel component takes the cluster data and does whatever it needs to with
> it (internal adjustments, recovery, etc).
> 
> 2. Each kernel component "foo-kernel" has an associated user space
> component "foo-user".  Cluster events (from userland clustering
> infrastructure) are passed to foo-user -- not into the kernel.  foo-user
> determines what the specific consequences are for foo-kernel.  foo-user
> then manipulates foo-kernel accordingly, through user/kernel hooks (sysfs,
> configfs, etc).  These control hooks would largely be specific to foo.
> 
> We're following option 2 with the dlm and gfs and have been for quite a
> while, which means we don't need 1.  I think ocfs2 is moving that way,
> too.  Someone could still try 1, of course, but it would be of no use or
> interest to me.  I'm not aware of any actual projects pushing forward with
> something like 1, so the persistent reference to it is somewhat baffling.

Right. I thought that the node manager changes for generalizing it where
pushing into sort-of direction 1. Thanks for clearing this up.



Sincerely,
    Lars Marowsky-Brée <lmb@suse.de>

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