Append and then Overwrite fills and ejects the tape

[Justin81]

Hi,

  We are using Backup Exec 12 Rev 1364.  Previously, we were running Full backups (Reset Archive bit) and that was fine but they ran for hours and hour so we were hoping to cut this down by using Incremental Backups.  Incremental backups were fine when we used them in conjunction with the Overwrite Media option but now that we have tried them with Append to Media, Overwrite if no appendable media is available, the the tape gets filled and then it is ejected.  The media tab says that the tape is filled to capacity but when I put the tape back in (regardless of whether or not I acknowledge the alert) it always pops the tape out again saying that the media is Overwrite Protected.  According to the Media Set properties, the overwrite protection settings are: Overwrite protection period: 0 Hours; Append period: None; Infinite - Allow Append.  The system confirms that Overwrite protection is set to None by telling me that 'The overwrite protection level for Backup Exec is set to NONE.  The media set's overwrite protecetion period will be ignroed and media will not be protected as long as the overwrite protection level is set to NONE.'   In the Alerts section, it says "Media 'Thursday02' is overwrite protected.  The media in drive IBM3 is currently allocated and is not available for overwrite operations.'  It then states that the Overwrite Protecion is set until 01/01/1900 00:00:00 and Appendable is set until 'Infinite - Allow Append'.  Can you tell me if this is down to an issue with the Overwrite Protection period or if it's down to something simpler such as the fact that the job is set to eject the tape when the job is complete?  Could it see filling the tape by appending to it as one job, eject the tape and then not be able to overwrite because the tape is popped out?

Many thanks,

Justin.

[pkh]

I don't understand why you would want to pop in the tape that was just ejected.  If BE had used it, then you would have overwritten the first part of the backup, thus rendering your backup useless.

When your job specify append, it will append to the first tape and then it would need overwriteable tapes for the the second and subsequent tapes.

Normally, we would leave the protection level to the default, partial, so that whatever OPP that is set for the media set is used.  Otherwise, we risk overwriting our tapes.

You should not be using a OPP of 0 as this affords no protection for yout tapes.  You should be using something reasonable like a few days.

When you are appending to tapes, make sure that you have a couple of overwriteable tapes on hand so that when the job needs another tape, it is available.

[Justin81]

Hi PKH,

     We have 2 series of 4 tapes which run from Monday to Thursday in a 2 week loop (so Tuesday01 and the rest of the 01 series tapes goes out off site, we get Tuesday02 in and use it, then Wednesday02 until Tuesday when the process repeats itself with the other series) backing up the file server, exchange server etc and several others.  On Sundays, using another tape, we back up a directory containing VM snapshots created by Vranger. Whatever about the fact that using an incremental backup, we won't have a full backup of everything in the case of a failure (we'll probably run a full backup on a scheduled job once a week to get a backup of everything), is it possible to set the tape to run, fill it to capacity and then start again when it reaches the end of the tape?  Since the tape is relatively large and the backups which are going to be written to it, alot smaller (since they're only incremental), we should be able to fit a few days onto each tape in case they need to be restored.  At the moment, the tape runs and when it's out of space, it is ejected.  Can the fill and restart operations be made into one job so that the job completes and we get a complete incremental job? In some cases, the tapes are full when they go in so in this case, shouldn't Backup Exec write to the start of the tape from the beginning or do I need to keep erasing the tape when it reaches capacity?  Would it help to uncheck Eject tape when job completes?

Also, I thought that the best Protection Period to start and troubleshoot with would be None since it's the least restrictive.

Can you advise?

Many thanks,

Justin.

[Ken_Putnam]

As PKH mentioned, if you fill a tape, and then succeed in writing to the beginning of that same tape, the first part of the backup (at the end of the tape) is no longer available (tho it is still physically on the tape)

Generally, to rotate tapes,you need at least two sets of tapes for each media set, and setup a scheme to overwrite, and then append, swap sets,and repeat.  For example you may have a media set called "Daily"  and have two sets of daily tapes.

Set your Monday job to Overwrite, and the rest of the week to Append.  When the tape fills up, BackupExec will continue onto Daily Set1, #2, if that tape fills up, it will use Set1, #3 etc

Then on the next Monday, you insert Set2.  BackupExec starts on Set2 #1, rolls onto Set2#2, then Set2#3 etc

If you have only two sets, the third Monday write to Set1#1 again.  if you have three sets use Set3#1

Set Global Overwrite to either PARTIAL or FULL, and if you have two sets of tapes, set the Daily OPP to 8 days, if three sets, to 15 days, etc

[pkh]

What you are trying to do is not possible.  When BE writes to a tape, it effectively erases the tape before writing to it.  Whatever is on the tape previously is gone.  For example, you have Day1, Day2, Day3 backups on a tape.  You start append Day4 backup on this tape and it ran out of space and BE eject the tape.  If you pop it back in and managed to get BE to write to to it, then Day1, Day2, Day3 and Part 1 of Day4 backups are gone.  It is not like what you imagine, that BE will just overwrite Day1 backup and keep Day2, Day3 and Part 1 of Day4 backup.

The Eject option plays no part in above.

As I said previously, you got to set your Protection Level to at least Partial for your OPP to work,  Otherwise, your tapes are vulnerable to accidental erasures.

[Justin81]

Thanks for the information.  This is going off the point if the job isn't suitable for our needs but, can you tell me, if the Append and Overwrite job could potentially get to the end of the tape during a job and then during the same job, start again at the beginning and erase the tape including the first half of the current job, then what use could it be of?   It's not working in any case at the moment, but I'm just wondering what scenario you'd use this job in? We don't have a robotic arm for the tapes, so, unfortunately, spanning overnight is not an option.  We put one tape in each night, Mondays to Thursdays and back up the files on the critical servers.  If we're going with a mix of Full and Incremental backups, would you suggest something like a Full backup on a Monday or Thursday using Overwrite and then Incremental backups for the rest of the Monday to Thursday days also using Overwrite?

Many Thanks,

Justin.

[Ken_Putnam]

No matter what scheme you come up with, if you do not have a loader, only a stand-alone drive, and the job exceeds the capacity of the tape on a routine basis, about all that you can do is upgrade to a higher capacity drive.  You can't even add a second stand-alone drive.   Symantec removed Cascaded Drive Pools (with v12 IIRC)

There is no way I know of to do any fancy stuff once a volume has filled up.  BackupExec will just sit waiting for an Overwiteable Tape or Cancel the job depending on what options you have selected

That being said

If you can get all the INCR for the week onto one tape, you could run an Overwrite as the first INCR after the FULL, with Appends the rest of the week. 

[pkh]

As I said earlier, if BE manages to re-use the tape that was just used and erase the first part of the backup, then your backup job is of no use.  How would you be able to restore from this backup when Part 1 of the backup is gone?

If you are using a tape library, then appending to a tape is easy.  Just make sure that you have sufficient number of overwriteable tapes in your library for the job to complete.

In your case, since you do not have a tape library, you have 2 choices

1) when the job requires a second tape, just let the job hang over-night until the next day, when someone can pop in the next tape.

2) give up on the idea that you can fill the tape up to the brim.  Just make sure that whatever you are going to write to the tape is less that the capacity left on the tape.  There will always be some unused capacity on the tape.

[Justin81]

Thanks for your responses - in that case, of what use is the Append and Overwrite backup job since you could end up with a backup which won't restore properly?

[pkh]

Let's say when you append to a tape and it spill over to a second tape.  If you keep both tapes, then you have a complete backup and you can restore from this set of 2 tapes.