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From Gregg Wonderly <gr...@wonderly.org>
Subject Re: datastructure classes
Date Fri, 17 Dec 2010 16:00:03 GMT
On 12/16/2010 8:09 AM, Sim IJskes - QCG wrote:
> On 16-12-10 14:55, Patricia Shanahan wrote:
>>> However, we should be able to do, say, hundreds of millions of
>>> transactions in a day in real-time critical systems such as the FAA
>>> or the stock market with data affinity and integrity and all the
>>> other "ilities". If Outrigger cannot do this, it is of no interest
>>> to us.
>>
>> The current record for a relational database doing simple transactions
>> is 30 million transactions per minute (Oracle/SPARC TPC-C). Your mileage
>> may vary, but there is no inherent limit on relational database scaling
>> that puts a few hundred thousand transactions per minute out of reach.
>
> Apart from that, it would be very interesting to see how a COTS DB backed
> javaspace whould behave in practice. And it could be the first step into
> producing alternative persistence mechanisms. In the early stage it would be
> comfortable to know we don't have to prove the correctness of a cots-db. In a
> later stage we can always look at lifting the transaction based blockstorage
> layer from derby or another java based db for instance.

One of the primary issues with bandwidth through any system is latency.  While 
multiprocessor/multi-core and distributed computing can provide huge bandwidth 
possibilities, the underlying issue is per transaction latency.

If you look simply, at the JDBC model for example, the act of converting the 
JDBC activities to network traffic and back (marshal/unmarshal) is one of the 
primary "time consuming operations".  When you add onto that other overhead 
associated with how each database authenticates and manages its "network" 
traffic.  I have no exact numbers to demonstrate this, but it is something which 
I have very long experience dealing with, over the years, with my broker (built 
before JMS existed) and catching up 100's of thousands of transactions into 
databases which have gone down for maintenance.

JDBC only allows one transaction per connection, so you have context overhead 
involved there.  With each transaction coming across a separate TNS-Listener 
process in oracle, you have OS context switching issues that inject latency.

Overall, the bandwidth can be very large, but the per transaction latency is 
probably the biggest reason that SQL databases are not always the best choice 
for some types of performance needs.

Gregg Wonderly

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