Backup size

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Backup size

Krasavita

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August 20, 2012 at 12:59 pm

#260314

Hello,
Before I run backup,can I check how big it will be?
Thank you

Viewing 6 posts - 1 through 5 (of 5 total)

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GSquared SSC Guru Points: 260824 More actions · Answer 1

Not really. You can get a general idea, in that it's usually smaller than the database (assuming free space in the data and log files).

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Alan Burstein SSC Guru Points: 61141 More actions · Answer 2

This will tell you the minimum size (the size of your MDF and NDF files). The backup, unless compressed, will never be less than this.

USE {myDB};

SELECT SUM(size/128) AS mb FROM sys.database_files WHERE type = 0

"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."

-- Itzik Ben-Gan 2001

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 3

Actually it probably will be.

That query returns the total size of the DB files. A backup does not back up the entire file, just the used portion of it. So if you have a 10GB database that's only 50% allocated, the backup will (ignoring contribution from the log) be around 5GB in size.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Alan Burstein SSC Guru Points: 61141 More actions · Answer 4

GilaMonster (8/20/2012)
Actually it probably will be.
That query returns the total size of the DB files. A backup does not back up the entire file, just the used portion of it. So....

Good catch. Did not think about unused space. :blush:

"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."

-- Itzik Ben-Gan 2001

SQL Show SSCertifiable Points: 6143 More actions · Answer 5

Use dbname

Go

Select count(Total_pages), count(used_pages) , sum( total_pages* 8) TotalPagesKb, sum(used_pages * 8 ) Usedpageskb from sys.allocation_units

I am not sure above query will help you 100%, but you may get an idea about of your backup size will be.