On 9/29/05,
Tino Wildenhain <
tino@wildenhain.de> wrote:
Well, I dont know why many people believe parallel execution
automatically means high performance. Actually most of the time
the performance is much worser this way.
If your dataset remains statically and you do only read-only
requets, you get higher performance thru load-balancing.
If howewer you do some changes to the data, the change has to
be propagated to all nodes - which in fact costs performance.
This highly depends on the link speed between the nodes.
I think you should clarify that the type of clustering you're discussing is the, "shared-nothing" model which is most prevalent in open-source databases. Shared-disk and shared-memory clustered systems do not have the "propagation" issue but do have others (distributed lock manager, etc). Don't make blind statements. If you want more information about "real-world" clustering, read the research for DB2 (Mainframe) and Oracle RAC.
--
Respectfully,
Jonah H. Harris, Database Internals Architect
EnterpriseDB Corporation
http://www.enterprisedb.com/