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Issue appending to tapes

Created: 10 Dec 2013 | 11 comments

Hello, I'm having a problem appending to tape.  I use a 24-Tape Robotic Library and I usualy run:

2 sets of week FULL backups jobs i.e. Week A, Week B.  They run over the weekend.  Next week I change the tapes for Week B and run FULL backups again then rotate again next week and so on with seperate Month tapes every 4 weeks.

During the week I run INCREMENTAL jobs to seperate tapes Monday to Thursday. I also have 2 sets a set for Week A and Week B.

How I usally have the Overwrite and protection set to for the FULL is: OVERWRITE 12 DAYS,  APPEND 0 HOURS with the job set to overwite the media so the are protected for almost a full week (although they won't be in the library the next week anyway) and can't be appended to.

The settings for the INCREMENTAL jobs are: OVERWRITE 30 HOURS,  APPEND 5 DAYS with the job set to Append if not Overwrite. This means that the tapes are free to overwrite sometime Sunday ready for the next week so they don't append to the tape (although the tapes should have been switched for the second week Incremental tapes to follow on from the new full backups anyway therefore making the 1.5 day protection pretty redundant.

The problem I've ran into a couple times now and never been able to find a solution is say when for some reason or other the weekend full backups fail to run to the point where I can't possibly find a window outside of business hours to re-run these backups and I want to continue appending to the previous week's incremental tapes as to have the option to restore from the previous week's full backup and say a week and a half worth of incremental jobs as a last resort.

I can't seem to find a set of protection rules that will allow me to append to the media.  What I'm trying to do is create a new emergency media set to apply to these Incremental tapes in this event.  I've even went to extreme values like:

Overwrite - Infinite don't allow, Append 1 Year

I'm assuming these rules should overide any previous media set and stop the media being overwritten but appendable for over the next year as the append time should be from the time of the first job???

My thinking is with this new media set my previous incremental ovewrite protection of 30 hours should be changed to never overwrite although my 5 day append should now allow me to append to this media again for a year from the first job??

I thought this would work the same way you change the media set to scratch and you can overwrite to media, so I assumed the new rules would overide the previous media set rules?

Please any help on what I'm missing here or got wrong would be greatly appreciated.

Liam Thompson

Operating Systems:

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pkh's picture

Yes. When you associate a media with a new media set, it will immediately use the OPP and AP specified in the new media set.  Hence what you are doing is correct.

However, what you are trying to do with your incremental backups is wrong.  When your full backup fails, you MUST rerun it to establish a new baseline.  You cannot just continue with your incremental backups.  I guess you are using BE 2010 or earlier because BE 2012 does not allow this.  If you are using the archive bit method, when the full backup fails, all the files that were backed up up till the point of the failure would have their archive bit reset and the subsequent incremental backup job will not be able to pick them up.  If you are using the modified time method, then all the files modified before the failed full backup job will not be picked up by the subsequent incremental backup job.

Liam Thompson's picture

Sorry I forgot to mention that the first backup stalled asking for a writable media therefore never starting the job or writing to the tape and the following jobs never started either due to being in the queue then cancelled.

I am using BE 2010

I am using modified time with change journal if that is any help.

Would this mean even if a backup kicked off waiting for a tape even if it was stuck in a queue behind 4 other job waiting for tapes that would never run the files would be flagged and altered?

pkh's picture

I am not sure when the job write the timestamp into the BEDB. To be save you should rerun the full backup

Liam Thompson's picture

Thats what I don't understand, surely if it does write and keep a time stamp from the previous media set (30 Hours overwrite, 5 days Append) and its ignoring the new "emergency extra append" media set (No Overwrite, 1 year append) it would have started overwriting the media as its been over 30 hours since the end of the last incremental backup?

pkh's picture

The timestamp I am referring to is the one written by your jobs because they are using the modified time method.  It has nothing to do with media sets or tapes.  If you want to know the gory details, read the section in the Admin Guide which explains how each of the backup methods work.

Suffice to say that you should rerun your full backup before continuing with your backup chain, regardless of whether anything is written to any media.  If any of your backups, full or incremental, fail, then you MUST do a full backup before continuing.  If you don't run a full backup, your backup chain will not have all the data that is supposed to be in them.

Liam Thompson's picture

Yes I understand that the timestamp isn't written to the tapes but is in association with the actual files to back up. 

Would you say that if a FULL job starts at the scheduled time but is queued for many hours behind say 4 other FULL backups due to an over running backup and I cancel said job so the tape never even loads into the drive that or creates/processes a snapshot the FULL backup still adds a timestamp stopping me from running the INCREMENTAL appending straight on from the previous week as if  I never tried to run ther FULL job?

I hope that makes sence?

Liam Thompson's picture

I have tried running the same incremental job twice in a row to a backup-to-disk folder using the same media set, exact settings just changed the destination from the tape to the folder and its working perfectly so for some reason the tape no matter what I do is telling me it can't be written to.

pkh's picture

This means that the tape is write-protected.

I am not being insulting, but I think you are getting confused because you do not have a clear grasp of the various concepts, like backup methods and media protection.  It might be better for you to read the Admin Guide and get a clear understanding before proceeding.

pkh's picture

The timestamp will not stop any backup. If the timestamp is written, then for all intents and purposes, the job is done regardless of whether anything is written out to the media.  Since you don't know at which stage of the job, the timestamp is written, why take the risk that your backup chain is incomplete.

Liam Thompson's picture

How can the media be write-protected the catch isn't pulled over nor are the media set rules set capable of stopping a job from writing to that media, that is the whole issue I've been suffering.

Liam Thompson's picture

Anyway the full backups are due to run tonight so everything should be back to normal, thanks for you help, I just needed to try and understand incase a simlar situation happens again as this is the first time in 5 years I've had this issue.