Query Performance Tuning - Expert Cube Development with SSAS Multidimensional Models - page 206

Designing for performance
Many of the recommendations for designing cubes we've given so far in this topic
have been given on the basis that they will improve query performance, and in
fact the performance of a query is intimately linked to the design of the cube it's
running against. For example, dimension design, especially optimizing attribute
relationships, can have a significant effect on the performance of all queries—at
least as much as any of the optimizations described in this chapter. As a result, we
recommend that if you've got a poorly performing query the first thing you should
do is review the design of your cube (along with the relevant chapters of this topic)
to see if there is anything you could do differently. There may well be some kind
of trade-off needed between usability, manageability, time-to-develop, overall
'elegance' of the design and query performance, but since query performance is
usually the most important consideration for your users then it will take precedence.
To put it bluntly, if the queries your users want to run don't run fast, your users will
not want to use the cube at all!
Performance-specific design features
Once you're sure that your cube design is as good as you can make it, it's time to look
at two features of Analysis Services that are transparent to the end user, but have
an important impact on performance and scalability: measure group partitioning
and aggregations. Both of these features relate to the Storage Engine and allow it to
answer requests for data from the Formula Engine more efficiently.
Partitions
A partition is a data structure that holds some or all of the data held in a measure
group. When you create a measure group, by default that measure group contains
a single partition that contains all of the data. Enterprise Edition and BI Edition of
Analysis Services allow you to divide a measure group into multiple partitions;
Standard Edition is limited to one partition per measure group, and the ability to
partition is one of the main reasons why you would want to use Enterprise Edition
or BI Edition over Standard Edition.