Incremental only backup scheme for cycling data

[TheGlennDavid]

Hi folks,

Here is the scenario:

Layout
We have a server that runs MS SQL.  Every day, SQL creates a single file bakup of the database, and deletes all backups older than 4 days of age. This result is a folder on the drive that always has 4 days worth of backups.

Objective
I want one copy of each backup file on tape.

Plan
Run an incremental backup on the folder every day.  Never run a full backup

Expected result
Each incremental backup will have 1 file in it,namely the backup file created by SQL that day, and nothing else.

I know this is an odd approach, and that incrementals are usually tied to fulls.  But, since 

A) I'll never need to reconstruct the whole folder, and 
B) The files are never edited once they are created

I shouldn't actually need a full? I know that BE can also handle direct SQL backups, but we to use SQL for the actual databse backups. 

Thoughts?

[VJware]

Full backup is required for the incrementals to run....synthetic backups could have been an option, however I dont think it would apply to these backup files...

[pkh]

You can run incrementals without running a full backup.

[TheGlennDavid]

Hi VJware and pkh,

Thanks for your quick comments.  I thought I should write back with the results, and since there seems to be some disagreement dive a little deeper into the mechanics of backups.

It worked.  I ran an inrcremental backup from a media set that had never run a full.  I ws able to successfully restore the data, and it didn't requrie any other media containing a full backup.  

VJ, this is my understanding on how backups work, please correct me if I'm mistaken:

Incremental backups (with archive bit reset) work by scanning every file in the targete folder, and reading the status of it's system provided Archvie Bit.  The archive bit exists and operates indepenent of Backup Exec.  

When a file is created, or is modified, it's Archive Bit is turned ON.  Incremental backups make a backup of every file that has it's archive bit set to on, and then disable the archive bit.

Thus, in the scenario I outlined above, where one file is created every day, one file is deleted, and no files are modified, a daily incrmental backup should yield a single file backup every day.  You mention that fulls are required for incrementals to run -- I'd be interested if you would expand on that, is there something I'm missing?

[Ken_Putnam]

You mention that fulls are required for incrementals to run -- I'd be interested if you would expand on that, is there something I'm missing?

If you specify INCR only, your first backup will grab every file that has the archive bit set, generally meaning a full backup

Then, as you say, every subsequent backup will grab only new or changed files

In a DR scenario, if you only do INCR jobs, you would need to restore the first and EVERY subsequent INCR go get your disk back the way it was before the failure

Generally one gets around this by doing periodic FULLS to establish a new base-line. (every week or every other week for example)

[pkh]

You have not missed anything.  Your understanding is correct and for your purpose you can just run incrementals without first running a full. Generally, it is the recommendation that you always run a full backup before running any incremental backups, but in your case it is not necessary.  Don't worry about it.  Go on with your scheme.