SQL Logs backup

Posted on 2014-11-21
Last Modified: 2014-11-24
Hi Experts,

I need some recommendation for SQL backup.
Now I make the backup with Symantec BackupExec and the Agents.
This works well.
Regarding the LOG Backup I have some questions.
I have an incremental Backup and a differential backup of it.
But do I really need a differential backup of the LOGS ? Because each two hours I take a incremental backup.
The FULL backup is every day in the evening.
Question by:Eprs_Admin
LVL 25

Assisted Solution

by:Lee Savidge
Lee Savidge earned 125 total points
ID: 40457006
I wouldn't do a diff backup if you're doing an incremental every couple of hours.
LVL 45

Assisted Solution

by:Vitor Montalvão
Vitor Montalvão earned 125 total points
ID: 40457010
I think you are confusing terms.
I have an incremental Backup and a differential backup of it.
There's no such thing as Incremental Backup in SQL Server. Differential Backups are backups of all pages changed since last Full Backup.

But do I really need a differential backup of the LOGS ? Because each two hours I take a incremental backup.
There's no such thing as Differential Backup of the Logs. Differential Backups are from Full Backup. Also in SQL Server don't exists Incremental Backup. I think you want to say Transaction Log Backups, right?
LVL 69

Assisted Solution

ScottPletcher earned 125 total points
ID: 40457787
>> But do I really need a differential backup of the LOGS ? Because each two hours I take a incremental backup. <<

It's virtually always the other way around: you don't need the differential backup that often, you need log backups instead.

A differential backup gets you back to that specific point in time only.  
Log backups can be used to recover to any point in time.

Differential backups can be useful if you have to make very frequent log backups -- say every 15 or 30 minutes.  Then you might take a differential ~12 hours after your last full backup.  That way, if you need to recover to a time 13 hrs after your full backup, you can apply the differential instead of restoring 180 to 360 log files to recover for the first 12 hours, then use logs as normal to get the last hour.
LVL 23

Accepted Solution

Racim BOUDJAKDJI earned 125 total points
ID: 40459923
In addition to above comments, an example of frequency to help you...

> 1 full backup per week (Ex: Saturday)
> 1 differential backup 6 days per week (Ex: All days but Saturday)

In case of strong log growth OR requirement of point in time recovery.  (FULL RECOVERY MODE)
> 1 log backup every 5 to 10 minutes all day, after FULL or DIFFERENTIAL backups, up to time before the next differential or full backup starts.

Tip: On later versions of SQL please make sure to use compressed backups (or alternatively backup on compressed drives) for faster recovery time.

Hope this helps.

Author Comment

ID: 40461578
ok, now I understand.
Of course in SYMANTEC you can have incremental and differential backup jobs of the DB.
I have set up one FULL per day and each 4 hours one DIFF.
But this is not neded more I think.
The LOGs I backup each 2 hours.

This is enaough for us.

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