Thursday, 20 November 2008

Azure Tables, Entities and Partition Diagrams

It's always nice to explain things with diagrams, no matter how bad the diagrams are :)

A picture of a Table

The following diagram summarizes how a table of NxtGenUG (a UK user group) Coordinators might look in a Table in Windows Azure Storage Services.

This diagram shows that Chris Hay and Allister Frost are coordinators for the Cambridge region of NxtGenUG, and that Dave McMahon and Geff Lombardi are coordinators for the Birmingham region of NxtGenUG.

I have scribbled with my crayons how this relates to tables / partitions and entities in Windows Azure Tables.

image

The key thing to note about this table is that regions are partitions (birmingham, cambridge). The row keys are unique within a partition (but not outside of the partition, Chris and Dave have the same row key). Combinations of Partition Key and Row Key are unique.

Scaled Partitions

The following diagram shows how this table might be scaled in Windows Azure using Table partitioning.

The key thing to note is that entities within a partition always remain together (i.e. reside physically on the same server).

However partitions may not necessarily reside together, hence why querying across partitions is slower than querying exclusively within a partition

image

Silverlight and Tables

So this is how the tables look in the back end of Azure. This is a great structure and I can see this is something that Silverlight Applications could heavily utilize.

A lot of Silverlight applications don't necessarily need the full blown power of SQL Servers, and really want to save simple data in the backend, and be able to retrieve.

I can see this table type structure really being utilized within Silverlight. The downside is that Silverlight can't access it directly (you need to go via a ASMX / WCF Service). As I have said before I'm not sure you want to be able to give direct access, however perhaps some sort of delegated authentication scheme could work?

I think this will require more thought???

1 comment:

Alex said...

Hi Chris,
Nice to meet you on Sat.

Ironically these diagrams are better than the documentation Microsoft supply and make a lot more sense!

Alex
(Devevening.co.uk)