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Full and Differential backups - Are Overwrite and Append Periods important?

ZTNetworks
Level 2
Hello all,

Like many others I want to do a full backup on Monday and then differentials until Friday. I have used backup exec for many years, but always doing full backups every night. I will admit I have some bad habits. Such as forcing the backups to overwrite every night, and just changing the tapes every day. I would create the media set and set the Append period to infinite and the overwrite period to zero. This allowed for the backups to go off literally without a hitch.

Now that I am trying to do things a different way, I want to know the importance of the overwrite and append periods. Ideally I am backing up to external 2TB hard drives that have plenty of space. We have 4 that we rotate once a week. Lets take Drive 1 for this example:

Week 1
Drive 1 - Monday: Full backup (300 GB of total space)
Drive 1 - Tuesday - Friday: Differential backup ( 20gb over the next 4 days)
Total Week 1 data usage: 320GB 

The drive is changed out, and lays in a safe for the next 3 weeks. For arguments sake we should have 1680GB of space left on the drive.

Week 4
Drive 1 - Monday: Full backup- I want this full backup to APPEND to the same drive, since I have 1680GB left to use.
Drive 1 - Tuesday - Friday - I want these to also APPEND to the same drive.

What I am trying to achieve is having multiple months worth of saved data on a single drive. Once the drive fills up, I than want it to overwrite the oldest Full and Differential backups.

I'm a little confused as to how I would achieve this. Any help would be very appreciated :) Thanks!
5 REPLIES 5

pkh
Moderator
Moderator
   VIP    Certified
Once the drive fills up, I than want it to overwrite the oldest Full and Differential backups

This cannot be done.

For B2D folders, the Low disk space threshold parameter controls the point at which backup operation is suspended.  For example, if you set the Low disk space threshold parameter to 5GB, when there is less than 5GB space left on the disk, the backup operation will be suspended until you free up enough space on the disk for it to continue.  If the disk is in a pool, then the backup is not suspended when the Low disk space threshold parameter is reached, but the backup operation will span to the next disk.

You should set your OPP and APP in such a way that the oldest file is re-used before the Low disk space threshold parameter is reached.

RahulG
Level 6
Employee

The first thing you need to would be create emai sets with proper overwrite protection period and append period. The append perios does not really ,atter if you have the max size of b2d file set to some samll valuce like 4 gig or 6 gb Eg if you have the backup to disk file set as 4 gb and if yu run a backup of 22 gb it is going to create 6 b2d dile and the last b2d file would be for 2 gid..if you run another job which is set to append it is going to apend to the b2d file which was 2 gb and then create new b2d files accordingly ..
  You need to check the setting about the overwrite operation by going to tools and options --media mangement
and see which media it is going to select for the overwrite job ... is it scatch media or recycleable media ---select the option as per you need and also set the low disk space tresh hold according as suggested by PKH

Ken_Putnam
Level 6
For disk based backups, I would recommend NOT using Append jobs, since all the BKF files in an "append family" share a common OPP, which is reset when the latest ine is closed

This means that you could conceiveable wind up with a disk full of files, none of which are overwriteable.

Also, if you want to fill the drive before overwriting anything, make sure that from tools\options\media management you have selected the option to "Use scratch media befoer overwriteable media in the target media set"

ZTNetworks
Level 2
Hmm,

PKH - Are you saying that I can set the over write protection to 2 months, therefore I would ensure that I have at least 2 months worth of fulls and appends, (which in this scenario equals 640GB worth of data) but still allow the backups to overwrite and append so the drive never gets full and fails the job?

Ken - What would be your suggestion then? If I couldnt append to the media it would just overwrite itself every time it was used?

Thanks for the help everyone :)

pkh
Moderator
Moderator
   VIP    Certified
What I am saying is that you should set your OPP and APP such that the total amount of data on the disk at any one time do not exceed the low threshold limit and fail your job.  You have a 2TB disk and your weekly backup is estimated to be 320GB.  If your Low disk space threshold is set to 50GB, you can keep 6 weeks worth of data (1920GB) without busting this limit.  To be on the safe side you might just want to keep only 5 weeks worth of data on the disk.  This is to cater for growth.  In this case, your OPP should be set to 4 weeks, so that on the 6th week, the first week data becomes overwriteable and could be used by the job.

What Ken is trying to say is that if you append to the .bkf files, the OPP is calculated from the end of the last append job.  Let's say your OPP is 4 weeks and you are appending to the .bkf files that were created in 1st.  When the 2nd week job append to these files, they will only be overwriteable in the 7th week.  Further, if your 3rd week job append to these files, they will be protected a further week.