[Lustre-devel] Commit on share

Alex Zhuravlev Alex.Zhuravlev at sun.com
Mon Jun 2 01:42:01 PDT 2008

there was an idea to control recovery postponing replies.
can we use this idea for COS? instead of immediate sync
we execute request, but put reply on a special queue. then
reply is sent from the queue when all previous transno
are committed (for COS w/o VBR). if there is no requests to
be handled, but reply queue isn't empty server does sync.
for VBR, the rule is a bit more complex - we'll have to track
dependency on per-object basis.

thanks, Alex

Peter Braam wrote:
> This HLD is definitely not ready at all.  It is very short, lacks 
> interaction diagrams and the arguments made are not sufficiently detailed.
>     * the second sentence is not right.  Commit should happen before
>       un-committed data coming from a client is shared with a 2nd client.
>     * Is COS dependent on VBR – no it is not, and can equally apply to
>       normal recovery
>     * Section 3.2 is wrong: the recovery process will not fail with gaps
>       in the sequence when there is VBR.  It only fails if there are
>       gaps in the versions, and this is rare.
>     * 3.3 parallel creations in one directory are protected with
>       different, independent lock resources.  Isn’t that sufficient to
>       allow parallel operations with COS?
>     * 3.6 provide a detailed explanation please
>     * GC thread is wrong mechanism this is what we have commit callbacks
>       for
>     * Why not use the DLM, then we can simply keep the client waiting –
>       the mechanism already exists for repack; I am not convinced at all
>       by the reasoning that rep-ack is so different – no real facts are
>       quoted
>     * It is left completely without explanation how the hash table
>       (which I think we don’t need/want) is used
> Regards,
> Peter
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