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.

Related Posts

Managing Central Management Server

Chrissy LeMaire shows how you can use dbatools to manage Central Management Server and registered servers: It’s a super useful feature that not all DBAs know about. Since CMS data is stored in msdb and accessible via SMO, you can access it from SQL Server Management Studio or PowerShell modules like dbatools. Central Management Server’s essential […]

Read More

Checking File Sizes In SQL Server

Andy Mallon looks back at a contribution by Junior DBA Andy, this one on checking file sizes: This is every DBA’s favorite game. Figuring out what DMV contains the data you want. It turns out there are two places that database file size info is maintained. Each database has sys.database_files which has information for that database. The […]

Read More

Categories

February 2016
MTWTFSS
« Jan Mar »
1234567
891011121314
15161718192021
22232425262728
29