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Understanding Overwrite vs Append

Created: 29 Nov 2007 • Updated: 21 May 2010 | 6 comments

    Hi,

We are running 11d (7170, sp1) on Win 2003 Server Standard.  We have two jobs running nightly, disk-to-disk and then clone-to-tape.  My question is regarding the tape backups. 

We have the tape job set to: Append to media, overwrite if no appendable media is available.  We have overwrite protection set to 6 weeks and append set to Infinite-Allow append.  We get "Please insert overwriteable media" errors for the tape jobs even though there are tapes in the library with room on them for the backup.  If we import an overwriteable tape the job completes.  All of the tapes in the library (before the import) are not overwriteable due to the 6 week limit.

My co-worker is insisting that Backup Exec is not working correctly. He is adament that job should use one of the tapes in the library to complete the job.  I think that this is not right.  I believe that if the tape is not overwriteable due to the Overwrite Protection period not  having been reached, the tape will not allow appends or overwrites.

Who is correct?  Do we have a problem (if so, it is most likely configuration and a mis-understanding of the overwrite/append concepts) or is BE acting correctly

Thanks for your help!

BeltwayBandit

Comments 6 CommentsJump to latest comment

Ken Putnam's picture
I believe that if the tape is not overwriteable due to the Overwrite Protection period not  having been reached, the tape will not allow appends or overwrites
 
90% correct.  the Overwrite period has nothing to do with Appends
 
The Overwrite period, during which BackupExec will not overwrite the tape, is figured from the time that the LAST data is written to the tape.  If you create the tape on Monday, and append Tues, Wed, and Thurs.  The OPP is reset at the end of the Thurs job
 
 
The Append period, during which BackupExec  will allow more data to be written to the same tape, is figured from the time that the FIRST data is written, and this never changes until the tape is ovewritten again

If this response answers your concern, please mark it as a "solution"

BeltwayBandit's picture

    Ken,

Thanks, for the reply, but I'm still not clear on this.  If the append period is set to Infinite-Allow Appends,will the Overwrite period not being expired not allow appends as well.  That is the crux of the argument.  I think that the overwrite period not being expired will not allow overwrites OR appends, my co-worker thinks that it will allow appends, but not overwrites.

That is the answer we are looking for.

Thanks,

Craig

Ken Putnam's picture
Your co-worker is correct.  As I said, OPP has nothing to do with Appending, OPP and APP are two completely separate things
 
If the tape is still within the APP, if the jobs specify the same media set, and if there is room on the tape, the second (third, fourth ...) job should append with no problems, within or after the OPP
 
But remember, if you DO append, the OPP is reset as of the time the last data is written to the tape.



Message Edited by Ken Putnam on 11-29-2007 07:55 AM

If this response answers your concern, please mark it as a "solution"

BeltwayBandit's picture

    Ken,

Ok, got it, sorry for the confusion.

Now, do you have any ideas as to why the job would be requesting overwriteable media, when the job is set to append and there are tapes available with space on them?  Could it be that BE is not selecting any of the tapes to append because there is not enough space on any one tape for the job?  I am under the impression that BE will use multiple tapes for the append if it needs to.

We have two tape jobs each night.  One is averaging about 120GB and the other hovers at around 230GB.  We have over 1TB of available space on the tapes in the library (and in the corrrect partition).  None of the tapes have expired OPP, so they are not overwriteable.  All of them have an APP of Infinite-Allow Append.  Yet we will get an error from the job asking us to insert overwriteable media. 

Why would we get this error?  Where should/can I look to make sure that everything is setup to allow the appends?

Thanks!

Joseph Gremillion's picture
Do you have appendable tapes within the same media set loaded in your library?  If you do not, then you will be prompted for overwritable media.
 
-Joe
BeltwayBandit's picture
Joe,
 
Yes, the tapes I refer to in my previous posts are in the same media set and partition of the library.  On the surface it looks like everything is setup correctly to allow BE to append to the tapes, however, BE will not try to append, it always asks for overwriteable tapes.
 
Thanks!