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DPChallenge Forums >> General Discussion >> Silly back up question, please help
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06/30/2006 04:14:13 AM · #1
I use acronis true image to backup my data. I have a backup of all my images onto an external harddrive. I now need to clear some space on my working harddrive and thus need to delete alot of old images.
My backup is set to run once a week to make a differential beckup (backs up only changes made since last back up). I suddenly got worried that if I delete images and then the backup runs again it will modify the backed up files (on the external hdd) and I will lose those deleted files.
I know that doesn't really make any sense but I got worried. Please calm me down :)
06/30/2006 06:36:46 AM · #2
Sounds like you need to check the settings for your backup software -- look for something that tells it what to do when a file in the backup isn't there anymore.

---

More directly to the point, but speaking more generally, a partial backup will usually only look at the 'dirty' flag of a file -- this is meta-data that is set when the file is created or modified and reset when backed up. A partial backup needs only look for and backup those files that have that flag set. A file that is no longer there will not be available to have it's flags inspected.

David
07/01/2006 06:21:31 AM · #3
Originally posted by David.C:

that is set when the file is created or modified and reset when backed up. A partial backup needs only look for and backup those files that have that flag set. A file that is no longer there will not be available to have it's flags inspected.

David


So if the original file doesn't exist anymore (and thus the flag) nothing will be modified in regards to that file in the backup?
07/01/2006 06:25:29 AM · #4
You don't have a thing to worry about. Automated backup software never deletes anything from previous backups, just adds to them or makes whole new sets, depending on how it's configured.

As far as I know, anyway. It's unthinkable to me that any backup software would remove from backup anything that's not currently on the disk being backed up, that would defeat the whole purpose.

R.
07/01/2006 07:03:28 AM · #5
I use SyncToy from MS to backup to an external HD.

With that software you have to be very careful with your settings, because in some cases if you delete a file from your C: drive it *will* delete from the external HD. Check your settings.

Best thing is to run a test. Create a file on your C: drive, do your backup as normal, then delete it and run the backup again to see what happens. That way you can be sure.
07/01/2006 03:20:50 PM · #6
Originally posted by Refwhett:

Originally posted by David.C:

that is set when the file is created or modified and reset when backed up. A partial backup needs only look for and backup those files that have that flag set. A file that is no longer there will not be available to have it's flags inspected.

David


So if the original file doesn't exist anymore (and thus the flag) nothing will be modified in regards to that file in the backup?

Yes, but check your backup software. Some backup utilities go beyond just making a backup an try to keep the duplicate exactly the same as the original (such as SyncToy which John mentioned).

Each backup software package has different option and does things a bit differently trying to get market share. The only thing to do is to become more familiar with how your backup software works. Read the manual/help files, perform some tests (again as John suggested) and learn what it does and how to control it.

David
07/01/2006 05:19:02 PM · #7
Then there are some which keep all versions of all documents until you instruct the software to delete them.
mydocumentsbackup.com

Message edited by author 2006-07-01 17:20:15.
07/01/2006 05:29:41 PM · #8
thanks for all the help. I will run a test. Like Bear said I can't imagin that it will do that since it's not a image ghost but rather a BACKUP software. I ust got worried.
Thank you.
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