[erlang-questions] Mnesia vs When Databases Lie: Consistency vs Availability in Distributed Systems

PatrickErj <>
Mon Dec 17 17:33:44 CET 2007


My bad on AWS, just checked RightScale EC2 tests:
http://info.rightscale.com/2007/11/29/network-performance-in-ec2-and-s3

Still the 75 to 350 microsecond latency in EC2 is a lot, for seriously busy
database even too much.


PatrickErj wrote:
> 
> That option costs min. one million dollars and the Facebook case is just
> lame. You will need 1Gbps link that is redundant and costs min. 40$/Mbps
> i.e. 45K$US/month let alone duplicate servers. Globally dis pared system
> is ok for doc's but not ok for HA/HPC DB. Also Amazon AWS does not cut
> well for "stock exchange" because you are talking about 10< microseconds
> and AWS is talking about 10< miliseconds in db transaction time, that is
> why Google has mapreduce.
> 
> 
> 
> 
> 
> Joel Reymont wrote:
>> 
>> How does Erlang change or improve this situation?
>> 
>> http://tinyurl.com/2745ha
>> 
>> I can't imagine a fragmented Mnesia table would help here, not when  
>> one chunk lives in Europe and another in the US.
>> 
>> I also imagine there would be significant costs in Transatlantic  
>> replication (in terms of transaction time, not dollars) if a regular  
>> distributed Mnesia table is used.
>> 
>> I want to dig deep into Mnesia for the corresponding chapter of my  
>> book. I plan to try to figure out and write up the distributed commit  
>> protocol, for example.
>> 
>> I think I'll also try to set up exactly the scenario that the above  
>> article describes (two machines, multiple Mnesia nodes) and simulate  
>> denial of service attacks, tripping over power cords, etc.
>> 
>> I want to know exactly how much network bandwidth is taken by  
>> replication among other things and what exactly happens when I bring  
>> up a Mnesia node that went down. There was a discussion of this  
>> recently but nothing beats a step by step explanation.
>> 
>> 	Thanks, Joel
>> 
>> 
>> --
>> http://wagerlabs.com
>> 
>> 
>> 
>> 
>> 
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://www.erlang.org/mailman/listinfo/erlang-questions
>> 
>> 
> 
> 

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