Rebuilding Indexes For Contiguity

SQL Sasquatch throws out an interesting question:  why would you rebuild an index which is 0.44% fragmented?

NC_TABLE1 is 36 total extents.  288 eight k pages.  2.25 mb. It can be read in 5 reads – one read for each contiguous run.
CI_TABLE1 is comprised of 48 extents.  3 mb. It can be read in 11 reads – again, one for each contiguous run.
The SQL Server instance has the -E startup option enabled.  Without that startup option, proportional fill algorithm would distribute incoming data to the 8 data files with a potential smallest allocation of a single 64k extent before rotating round-robin to the additional files in the filegroup.  With the -E startup option, the smallest possible new allocation by proportional fill is sixty four 64k extents – 4 mb.
That means if I can rebuild the indexes into new space at the tail of the files, the contiguity should be improved considerably.

I had never considered that the scenario described here before, so this was definitely interesting.

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