Back-up question

Posted on 2006-07-19
Last Modified: 2010-04-03

We recently bought Veritas Back-Up and I want to use it to do a full back up once a week, and then just back up the changes to the files everyday. Then every weeek I will change the tape.

That's two jobs:

*New tape goes in every Friday.
*First job = full back-up, overwriting anything that's there.  This be on Saturday, when no-ones here.
*Second job, runs every day,  Monday to Friday in evening, records changes. Do I use differential or incremental. What's the difference? Anyway, this job will always append.

Come Friday, tape is ejected. This should contain one full back up file and five changes back-up file.

Does this sound good?

Question by:Jason210
LVL 18

Expert Comment

ID: 17137798
Here is a quick read about the differences between differentials and incremental backups:,295199,sid63_gci982396,00.html

I would recommend differentials as the restore only requires the last full backup and the more current differential as opposed to incremental where you need the latest full backup and ALL incrementals till current.

I would also recommend keeping the full backups and differentials on different tapes. This way you know that once the full back is successful you put it in a safe place and it is there if you need it. You don't want to risk the differential backup compromising your full backup.

Expert Comment

ID: 17138166
What way do you archive your backups, I would suggest that if you want to keep your backups safe from domestic and environmental hazard you should probably look into having a company backup tapes remotely. This way if anything does happen you will have a secoundary disaster recovery consingency plan should the owrst happen, their service often comes with collectiona nd delievery. Just something to look into.
LVL 16

Expert Comment

ID: 17138718
No, it does not sound good at all.
Suppose you have a fire on Thursday and need to restore from tape???

Also, restoring of data could be a nightmare.

Backup the entire drive -- or critical files only if you prefer -- every day.
Keep one tape offsite.
That way you have FIVE complete copies of your backup
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LVL 11

Author Comment

ID: 17139101
OK. Thanks so far...

Glenn, that sounds professional but it means a lot of extra work. Worst thing is someone has to go in the server room every day and change the tape. That's a problem because the server room is on another floor, and it needs a special security  key to get in there. I'm not on site to do it more than once or twice a week. May be two tape drives?

glenn >>Also, restoring of data could be a nightmare.

LVL 18

Expert Comment

ID: 17139146

2 tape drives would be a great idea, and if its in your budget I would say go for it. That would allow you to keep the jobs on seperate media and you would have less intervention. But that still leaves the full backup on-site...

Accepted Solution

callit earned 300 total points
ID: 17146681
I think in many cases daily full backups would be overkill - but this really comes down to what you're backing up.  You need to decide how much of a loss you're willing to accept.  

For instance, as mentioned above, if you lose a full backup, is it acceptable to go back to the previous week's full backup?  We have different backup policies based on our individual clients needs and abilities.  Some clients do a full backup at the end of every week, with a differential backup in the middle of the week.  Some have differential backups nightly.  Some have bi-weekly full backups - it all depends on the needs of the organization.

My recommendations (based on the information you've given) - don't append your differential to your full backup.  Get your most recent full backup off site in case of catastrophy. If you're archiving backups, consider getting a fire proof safe/box. As for your differential backup, do what you feel is best, again remembering that you have to determine how much data loss is acceptable.  If you only want to have to change tapes once or twice a week, go with your weekly full backup on the weekend, then change the tape monday morning, and let it do differential/incrementals all week. Then come friday, swap out your differential/incremental tape and drop in the new weekly full backup tape.  If you can get in in the middle of the week, consider going to a third tape if necessary; for instance, swap your differential/incremental tape for another on wednesday.

As for your question of incremental vs. differential backups:  Incremental backups back up any changed file since the last backup.  Differential backups back up any changed file since the last FULL backup.  So, with differential backups, the jobs might take a little longer, but if you're doing weekly full backups, you shouldn't have any trouble unless you're dealing with massive amounts of changing data which I doubt is the case since you're doing your full backup on one tape.  

If you need to restore with incrementals, you have to restore the full backup, then every incremental backup up to the most recent.  If you need to restore with differential backups, you only need to restore with the full backup and the most recent differential.
LVL 11

Author Comment

ID: 17279121
Thanks - makes sense.

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