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Differential Jobs retentions

Created: 14 Mar 2012 • Updated: 23 Mar 2012 | 12 comments
Sirconfluge's picture
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Hi

Can you please help with the below:

We have a tape drive (1 tape ,1 drive , tape size 400GB/800GB)... We want to take the file server with a differential backups daily from Monday till Friday. The File server size is 650GB, lets say we will need 1 full tape the first time we will run the differential backup because the Backup exec will take a full copy first time, the second day we will insert a new tape to run the differential job...

 

Question1: Since it is a new tape, Backup exec will be able to take only the difference from the last day or it will take it again as a full, because the last backup is on another tape?

If we are testing this scenario on a B2F it will take a full backup every time we change the B2F, is it the same for tapes?

 

Question2: If we want to restore from a differential backup in our case we will need 2 tapes (the differential backup and the full backup) is it duable if we have a tape drive (1 tape, 1 drive)?

Can we load the 2 tapes in this scenarion? or can we copy the content from tape to disk then do the restore?

 

Thank you in advance.

 

Comments 12 CommentsJump to latest comment

CraigV's picture

Hi,

 

1. Once you've run your FULL backup for the week, every other job on the number of days selected will be DIFF. So even if you use a new tape, the data that gets backed up is only the changed data. BE doesn't care about it being a new tape at all. This in no way affects the data being backed up.

2. Either way, if you duplicate the data to disk you're going to need those tapes as you'd be duplicating your data from the FULL backup, and then any changed data. Doesn't matter if you choose to do it this way, or restoring directly from tape.

Thanks!

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RahulG's picture

Answer 1: When you run backup , you set the backup job by using archvie bit or modified time , so if you run a full backup it will reset the archvie bit and next time when you run the backup it will only the backup the files which as the archvei bit reset . Same goes with modified time < backup exec checks the time modified time on the file . So the differential backup looks for the files which are moddified or chaged and not the actual backup media on which you have the full backup job 

answer 2 : when you restroe you need the tape which have the full backup and the tape in which you have the differential backup . When you run the restore it will prompt you to inser the approriate tape which holds the backup . 

Sirconfluge's picture

Thank you for your replies.

But if Backup Exec doesnt care about the location (tape or disk) why sometimes if we create a new B2F and redirect a job to it, the first backup on the new location is full even if the job is differential?

CraigV's picture

...are you using the same media set?

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CraigV's picture

...unless BE looks at something in the B2D catalog, and with it not being there in a new B2D folder, it runs the backup as a FULL again!

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Sirconfluge's picture

Adding everytime a new tape, is the same as creating a new B2D and redirecting the jobs to it..Right?

So it may not take a differential job Right?
Thanks again

 

CraigV's picture

No...I've seen it work with tape. Something else must be going on there if it tries to run a full backup every time you change B2Ds, unless this is by design according to the way it stores the catalogs and information in the B2D.

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Sirconfluge's picture

I have one additional question if you can help, normally when backing up on disk lets say we have a job with a retention 2 days and a size of 100GB

on the first 2 days, the size allocated on the storage is 200GB, the third day the job will run and will reserve on additional 100GB (the space allocated will be 300GB), once the job is completed it will overwrite the existing one(the space allocated after the 3rd job gets completed is 200GB), so if we are calculating the allocation space we should always take into consideration to add a space for one copy before applying the retentions.

Is it the same concept for tapes also?

Thank you for your help again...

RahulG's picture

Ideally you should consider tape as a bkf file and not backup to disk folder . When you run backup to disk it created several bkf , which you can relate as tape in a library . When you run a overwrite job on the backup to disk folder it does not overwrite the whole backup to disk folder but a bkf files , and if there are no overwritable bkf files then it creates new bkf file .

Sirconfluge's picture

Yes i understand ... but the question is what will happen before the overwrite will starts, it all add the new bkf once the job compelted it will erase the old ones?

Thanks again...

CraigV's picture

If your media isn't overwritable, then Backup Exec creates new files until your current media is either manually erased, or overwritable.

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