Required free disk space for SQL Server backup operations

_{Monday, February 4, 2008 5:16 PM}

What is the percentage of FREE disk space that is needed for a backup?  I have backups that are failing with no disk space errors.  But there is enough disk.  Does SQL Server need a percentage of free space all the time?

Thanks

geri

_{Tuesday, February 5, 2008 7:43 AM ✅Answered}

ok - so if your backup is 121GB and you only have 40GB of free space on the drive, how do you expect that to work? I'm not trying to be funny here - it seems like a very simple case of you not having enough space for the backup. Free up some space or put the backup on a different drive.

_{Monday, February 4, 2008 6:36 PM}

There's no minimum percentage - just that amount required to store the backup. How much disk free space do you have and how large are the backups usually? Note that backup size can vary (for all backup types) depending on a variety of factors so it may be that the backup you're trying to take is much larger than normal.

_{Monday, February 4, 2008 9:10 PM}

It appears that I 'run out' of disk space during a backup but when I look at the drive structure inthe morning - i have 40gb free.  One of the db's that is being backed up - it 121gb.

Thanks

g

_{Monday, February 4, 2008 9:13 PM}

That makes perfect sense - the backup doesn't check the available disk space before it starts. It continues until it takes up all the space, fails, and then deletes the file. Depending on how much space inside the 121GB database is actually used, you may need up to 121GB to back it up (at least using SQL Server's native backup).

Have you successfully backed up this database (at this size) before? If so, how big was the backup file?

_{Monday, February 4, 2008 10:05 PM}

Yes we backup this db every week.  And have another one that is larger than this.  Does SQL Server need some 'elbow room' while it is backing up?  We are using SQL Backup from Redgate for the backups.  Could I be barking up the wrong tree and should i be talking to Redgate?

Thank you for your time....

g

_{Monday, February 4, 2008 10:08 PM}

Again, how big is the database backup usually?

SQL Server doesn't need any elbow room - I think you just don't have enough disk space for the backup.

_{Monday, February 4, 2008 10:28 PM}

121 gb for one db

.5 to 3 gb for 5 others,

and .5 to 8 gb for 800 other dbs.

Then you have roughly the same number of log backups as above.

g

_{Monday, February 4, 2008 10:30 PM}

ok - the 121GB is the size of the database (as you mentioned earlier). How big is the backup of that database usually?

_{Tuesday, February 5, 2008 3:12 AM}

Nope that is the size of the backups as created by SQL Backup by Redgate.  The one database is at 650gb. The other db's full data size are from .5 to 40gb.  We are supposed to get 50 - 75% compression from the Redgate software.

g

_{Thursday, February 14, 2013 10:45 AM}

Just connect with your database and excute SP_SPACEUSED , and look the RESERVED column value, Your backup will take aprox that mach of space.

Regards Vikas Pathak