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Asked: 2026-05-17T00:59:50+00:00

I am trying to understnad how SQL Server allocates and reserves space. Having run

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I am trying to understnad how SQL Server allocates and reserves space.

Having run the examples from the article “How table design can impact your SQL Server performance?” [1], I received the results [My 1.1] diverting from those in article [1.1].
Why?

Why in one case the excessive space is reserved/allocated (all cases in [1]) but not in another [My 1.1]?
(Note that in [1] in both cases the excessive space is reserved, though on my computer only in one of cases)

How is space allocated, reserved by SQL Server?
And how can I control/manage it?

[1] ======
How table design can impact your SQL Server performance?
http://sqlserver-training.com/how-table-design-can-impact-your-sql-server-performance

[My 1.1]
My results diverting from [1] below 

name                               rows  reserved  data     index_size  unused
---------------------------------- ----- --------- -------- ----------- ---------
Fixed_Lenght_Row_Table_Optimised   10000 40008 KB  40000 KB 8 KB        0 KB

[1.1]
Results in [1] diverting from mine above

name                               rows  reserved  data     index_size  unused
---------------------------------- ----- --------- -------- ----------- ---------
Fixed_Lenght_Row_Table_Optimised   10000 40072 KB  40000 KB 8 KB        64 KB

[1.2]
Results from [1] coinciding with mine

name                                 rows  reserved  data     index_size  unused
----------------------------------   ----- --------- -------- ----------- ---------
Fixed_Lenght_Row_Table_Non_Optimised 10000 80072 KB  80000 KB 8 KB        64 KB
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1 Answer

  1. Editorial Team

    The article in the link is dubious at best. Does not specify what SQL Server version to use, and what are the various options enabled/disabled. Since SQL Server 2005 there is row small-lob storage for columns over spilling the 8K limit (see Table and Index Organization), there are default in-row vs. out-of-row options (see sp_tableoption) and there are many compression options (row-level, page-level, Unicode).

    For accurate information I would stick to the official product documentation, starting from Planning and Architecture (Database Engine). For a more digestible read, buy one of the well established books, like Microsoft SQL Server 2008 Internals or Inside Microsoft SQL Server 2005: The Storage Engine.

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