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I've been doing backups of my SQL Server 2014 Express databases for import to other servers and noticed a difference in file size between .bacpac and .bak.

Why is a .bacpac file so small compared to a .bak file of the same database?

Thanks for any insights!

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41

A

  • .bacpac file = Schema + Data. Note that Data is BCP'ed out using Native format (not readable by Human).

    • You can rename the .bacpac to .zip to see the actual contents.

    • You can use ...DAC\bin\sqlpackage.exe commandline to extract the .bacpac contents programatically.

    • It is a snapshot that includes User data + Schema from SQL Server or Azure SQL Database.

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  • Backup (commonly have .bak extension) = A FULL database backup contains a complete copy of database and provides a single point-in-time to which the database can be restored. A full backup contains some transaction log records so that the restored component (database, file, or filegroup) can be made transactionally consistent.

A BACPAC is not a substitute for a FULL backup. Its just a snapshot that can be used to move a database from one server to another (or to cloud) and archiving an existing database in an open format.

From my test, below are the results

enter image description here

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  • 3
    So what information is the .bacpac missing that the .bak file has, that makes it smaller? – AllTradesJack Dec 2 '16 at 17:17
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    The log file is probably the biggest reason for the size difference. – Paul Spangle Feb 17 '17 at 14:26
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    I'd assume there's no index data in the .bacpac either, which is likely to be a BIG contributor to file size. – Rory Mar 13 '17 at 10:42
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    In that case, when you restore from .bacpac do you need to rebuild the indexes somehow, or is this done automatically? – jocull Mar 16 '18 at 13:27

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