backups

[cptkirkh]

Which is the best to set the archive bit when backing up or to leave it alone. I am trying to figure out which is best and why. The reason i ask is my backup software will allow differential backups or incremental one's. The difference is how the archive but is set.

 

[Gazt]

Some backup software will allow you to do a 'copy' backup.

This will backup all data but leave the Archive bit alone so your normal backup schedule will not be affected.

Differential also leaves the archive bit but you only get the data that has modified since the last normal backup (normal resets the archive bit, a modify will set it).

Incremental resets the archive bit, you only backup the data that has been changed since any backup. To restore you would need the last normal backup and all subsequent incremental media up to the point of restore.

Hope this answers your question.

Gaz

 

[rbirt]

Another difference is how much time do you want the system to be down while you do a restoration. With incremental like Gazt said just backs up the data that has changed since your last normal backup. Which means that in order to restore your data you need to restore the last normal backup and then the incrementals are restored in the order of backup.
Normal backups backup all of your data, and then reset the archive bit.
Copy as Gazt said just copies the data without doing anything to the archive bit.
The big difference between Normal and Incremental is in the time it takes to do your backups and the amount of tape space used. Normal backups take the most time to restore a system, but less time to do your restoration. Incremental takes less time to backup the data and more time to restore because you have more tapes to restore from.
It all depends on how much time you want to spend on doing backups and how much time you have to get the system restored. Where I now work we use all normal backups, I do a full normal backup on Friday night and then during the rest of the week I pick and choose what data I want to backup. Since most of the time the system data does not change much and I make sure that our backup tapes have the most recent data on them. Also instead of having four tapes to do restoration from if my system fails on Thursday, I only have two tapes to backup from.
It all comes down to how much time can your business be without a system while you are doing a restoration of that system, and also test do test restorations to see if you actually have good data on your tapes and to see if the system is actually backedup. It will save you a lot of headaches down the road.
I hope this answers your question.