Jim Cook wrote:
> I can't talk from experience, and I am always highly skeptical of
> marketing
> fluff, but according to their docs, Gemstone uses their persistent cache
> to
> store stateful session bean state.
>
[Randy Stafford] Stateful session beans in GemStone can implement
the session synchronization interface and store session state however they
want - over JDBC connections, or over GsSessions (i.e., to PCA).
> I tried to stay away from bashing either vendor on the concept of
> failover,
> except where it is painfully obvious that a design flaw exists ;-) Any
> time
> you are serializing state across VM boundaries you will take a performance
> hit. I don't have any first hand experience with Gemstone's persistent
> cache
> architecture, but I would expect it to react to scalability in an
> exponential manner. The more nodes I add to the PCA, the more
> serialization
> necessary to keep these in sync. I am assuming their is a good balance to
> be
> found between failover and performance.
>
[Randy Stafford] The use of PCA doesn't require serialization
between VMs. All VMs (including servlet engine VMs) have direct access to
PCA via the class GsSession and a shared-memory architecture. GemStone is a
JVM source code licensee - we get the JVM source from JavaSoft and patch in
about 40K worth of hooks to the shared page cache mechanisms that implement
PCA.
Best Regards,
Randy Stafford
Senior Architect
GemStone Professional Services
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