[Drbd-dev] How Locking in GFS works...

[Lars Marowsky-Bree]

On 2004-10-04T17:12:24, Lars Ellenberg <Lars.Ellenberg at linbit.com> wrote:

> but yes, I think a consistent arbitration would do the trick much
> cheaper.

For two nodes yes. I think it's the optimal scheme assuming that write
contention is not the regular case; if a large percentage (>40% or so)
of writes would overlap I assume a coordination algorithm would be
better. But, I assume such workloads have a much more fundamental
problem. ;-)

> though for the (N>2)-node case I'd like to see your paper first ;)

I don't think this scheme will work well for >2 node active scenarios if
all more than two try to write and receive all writes in different
ordering.

But >2 nodes would likely wish to have an efficient multicast protocol
anyway. Three you could do in a triangle, but 4 already would suck for
such a full mesh anyway.

Actually, the 2-node active:active seems so straightforward it may make
sense for 0.8 already. A passive replication to more than 1 standby may
also be doable. >2 node active/active is 0.9 material...

I need to add that to our funding plans ;-)


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

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