High availability email server...
dave64 at andrew.cmu.edu
Tue Aug 1 08:41:50 EDT 2006
Daniel Eckl wrote:
> Hi Scott!
> Your statements cannot be correct by logical reasons.
> While on file locking level you are fully right, cyrus heavily depends
> on critical database access where you need application level database
> As only one master process can lock the database, a second one either
> cannot lock the database or just crashes it with simultaneous write
> access. I didn't try it by myself for obvious reasons...
> If that didn't occur to you, then you had incredible luck, that there
> was no situation where both processes wanted to change the same db
> file simultaneously.
Scott is not just lucky, he's using clustering technology that works.
When using a cluster filesystem that works, the locking semantics across
cluster nodes will be the same as those on a single node filesystem.
What you say above is simply not correct.
University of Pittsburgh is also running a 4-node active/active cluster
using Veritas Cluster Filesystem and it works very well. The
performance is incredible, and as Scott pointed out you don't need the
complexity of murder or application-level replication. Using a cluster
instead of Cyrus murder gives you both scalability and redundancy. The
big tradeoff is that Veritas Cluster Filesystem costs money, while Cyrus
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