backups prompting for another tape

[Matt26]

i'm using Backup Exec 11d Service Pack 5 on a windows advanced server 2000 SP4 server (domain controller) to perfrom nightly backups.

we have our media policy set to the following:

overwrite protection period: 0 hours

append period: infinite - allow append

each of our backup jobs has its properties set to:

append to media, overwrite if no appendable media is available

i'm noticing that in a number of cases the backup jobs will halt after they have been running for a period of time, the tape will eject and it won't continue until i insert another tape.. when i check the alerts, it notes a prompt for writable media.

i might be confused here, but shouldn't our media policy and backup job properties force the backup job to start overwriting existing data on the first tape if the backup is unable to append data to the tape?  this is what we want our backups to do.

this doesn't happen to all of our backups every night- we have about 6 jobs that run nightly, and i think it has happened with most of them at one time or another.

any help is greatly appreciated.

[Ken_Putnam]

 might be confused here, but shouldn't our media policy and backup job properties force the backup job to start overwriting existing data on the first tape if the backup is unable to append data to the tape? 

Since tape is sequential access storage , not random access, overwrite is all or nothing.  Once you re-write the tape headers, either by re-labeling or doing an overwrite job, the data on that tape is (for all intents and purposes) gone. 

You can still access with special programs, and data recovery services will  be glad to charge you for this, but standard end-user software cannot read anything previously written to the tape

This is why append jobs will only accept a (different) overwriteable tape when the first append volume fills up

[Matt26]

thanks for the response.

i'm not sure if my post was misunderstood, but i'm just trying to understand why the data can't continune to be written (in this case) over the existing data on the tape- i'm not trying to recover anything.

what i want is to have our backup jobs write to the tape being used, and if it there's no room to append data to the tape, overwrite the existing data on the tape, starting with the oldest data on the tape- is it possible to do this, and if so, how do i set this up?

i thought this was the way our backup jobs were set up to run but apparently i'm missing something.

thanks.

[Ken_Putnam]

what i want is to have our backup jobs write to the tape being used, and if it there's no room to append data to the tape, overwrite the existing data on the tape, starting with the oldest data on the tape- is it possible to do this, and if so, how do i set this up?

BackupExec does not do any kind of capacity check when selecting what tape to use.  It merely looks at the media set that a tape belongs to, whether it matches the media set in the backup job and if so, is the tape is still within the APP period

If all this matches, BackupExec will start appending data

When that tape fills up, it will ONLY continue as overwrite on another tape.  As I tried to explain earlier, if it went back and started writing to the beginning of the same tape, all data  backed up to that point would be non-retreivable.

[pkh]

When BE writes to the first tape, it will either overwrite the tape or it will append to the tape.  This depends on the OPP, AP and whether the job is set to overwrite or append

Assume that your tape capacity is 100GB and there is already 30GB on the tape.  Your job is writing out 150GB of data.

Overwrite - 

If BE overwrites the tape, then it will write the first 100GB of data onto the tape, wiping out the 30GB that is already on the tape.  It will then eject this tape and prompt for a second tape.  When you put in a second tape, BE will OVERWRITE the second tape and write the remaining 50GB onto the second tape.  BE will never append to the second or subsequent tape.

This is what appears to be happening to some of your jobs.

Append -

If BE appends to the tape, it will write the first 70GB onto the tape.  The 30GB that is already on the tape will remain.  BE will then eject the tape and request for a second tape.   It will then OVERWRITE the second tape and write the remaining 80GB to it.

Suppose the amount of data is 80GB, instead of 150GB, which can fit into the tape if it is overwritten.  In your case, your job will still append to the tape, write 70GB on it and then prompt for a second tape to write the remaining 10GB.  This is because your job specifies append and the first tape is appendable.  It will never overwrite because this is the fallback position if there is no appendable tape.

[Matt26]

thank you for the explanation.

this presents a bit of an issue for us, as we encounter this situation (a second tape being required to complete a job) on a regular basis... the reason that this is an issue is because we have our backup jobs set to run after hours (overnight) and of course, we're not here to change tapes if needed, so i discover the next morning that a backup job is hanging because it's waiting for a second tape- this is what i want to avoid.

so what is the best approach to avoiding this situation?  we don't really have the option of minimizing how much data we're backing up, so is this something that can be handled more effectively by changing our overwrite and append policies?  is the capacity of the data tapes a consideration?  we're using HP 400GB LTO-2 Ultrium data tapes.

[Ken_Putnam]

so what is the best approach to avoiding this situation?  we don't really have the option of minimizing how much data we're backing up,

If you are doing Append jobs you have two options:

1)  Change to all Overwrite jobs and purchase more tapes

2)  Upgrade your tape drive to a higher capacity drive and purchase a bunch of new tapes

If you are already doing Overwrite jobs, all you can do is upgrade the hardware

[pkh]

In addition to what Ken said, you can also invest in a new tape library which will allow you to backup to multiple tapes without manual intervention.

[Ken_Putnam]

{slaps forehead}

Doh!