SOA - Availability vs. consistency

SOA - Availability vs. consistency

• R.Tutus

  Well I was listening to Vogels (CTO of amazon) as he was describing amazon's internal architecture as purely service oriented. Then he went on to say that they have to consider trade offs such as availability vs consistency for each service.

  I think what he was saying is that they don't run 2 phase commit trx across all thier services. Rather they have to decide which services needed 2 phase commit and sacrifice availability to achieve it. Again, this is just my guess.

  So I'm not sure about any of this, and was hoping that someone who has worked on large scale soa would jump in and describe the various tradeoffs an architect needs to consider when architecting a soa system.

  Thanks

  Houman

  
  

• Demchuk

  That's great info. Do you know where I could get to see some of thier arch. presentations Or for that matter, any large scale soa system.

  Thanks

  Houman

  
  

• Sharad Birajdar

  No, the presentations were at conferences so I'm not aware of any publically available ones. Here's what I found on MSDN searching for SOA Case Study. I'm sure there are more around but this is a start.

  http://msdn2.microsoft.com/en-us/library/ms954622.aspx

  http://msdn.microsoft.com/library/default.asp url=/library/en-us/dnbda/html/sessfin00.asp

  http://msdn.microsoft.com/library/default.asp url=/library/en-us/dnaspp/html/aspnetscal.asp

  
  

• Manoj Agrawal

  That's great. Thanks!
  

• pjtaylor

  Can you provide more details about what you're asking
  
  

• Khenat.Ram

  I've seen several Amazon architecture presentations. They never use 2 phase commit because it would jeopardize availability if one of the databases goes down in the middle of a transaction. They keep multiple copies of their critical data and these copies are updated asynchronously. This means that failures might result in some temporary data inconsistency because a all the copies aren't the same but the multiple copies ensure that no data is ever lost. The chances of failures are low enough that the risk of temporary inconsistency that may be caused by a failure is not big enough to make risk of unavailable data caused by using 2 phase commit to guarantee consistency not worthwhile.
  

• Amadrias

  Houman,

  with respect of trade-offs and considerations, I'd suggest you the following resources

  • Principles of Service Design: Service Patterns and Anti-Patterns (article)
    http://msdn.microsoft.com/architecture/default.aspx pull=/library/en-us/dnbda/html/soadesign.asp
  • Service Orientation in Enterprise Computing (article)
    http://msdn.microsoft.com/architecture/default.aspx pull=/library/en-us/dnbda/html/soa_vb-1.asp
  • MSDN Architecture Webcast: Connecting Your Business with Service Orientation (webcast)
    http://msevents.microsoft.com/cui/webcasteventdetails.aspx eventid=1032275449&eventcategory=5&culture=en-us&countrycode=us
  • Demo of SOA application (webcast)
    http://channel9.msdn.com/ShowPost.aspx PostID=38823
  • Enterprise SOA Application Demo (download)
    http://www.microsoft.com/downloads/details.aspx familyid=e9fb6415-42aa-4a0e-9a7b-6966c9dc17f5&displaylang=en
  • Readings in Service Orientation (free eBook)
    http://msdn.microsoft.com/architecture/default.aspx pull=/library/en-us/dnbda/html/RdSrvOrt.asp

  Also, check the MSDN Architecture Center at http://msdn.microsoft.com/architecture

  
  
  

• Derek Nedelman

  Thanks for sharing this! I'm going to go through all of these.

  Regards,

  Houman

  
  
• SOA - Availability vs. consistency