Backup Exec 2014 Tape Overwrite Protection query

[LozBC]

Hi,

I have two tape Media Sets.

Full Backup

Daily Backup

Both have their Overwrite Protection Period set to 12 weeks.

I use differentials Monday ,Tuesday, Wednesday ,Thursday and Fulls on Friday.

This has been working fine, and I have had a large batch of LTO tapes to use.

I am now running out of unused tapes and am looking at re-using some of the already allocated tapes. Fortunately I have had enough tapes for 16 weeks so some are now overwritable.

Looking at the Offline Media section I can see that Backup Exec is correctly allocating the overwrite date (I have a large range of tapes which are overwritable).

What I am wondering is does Backup Exec do anything regarding the full backups in regards to differentials?

For example I have the following:

Friday Full Tape	Allocated 12/12/2014 18:02	Overwrite protected until 07/03/2015 03:13
Monday Differential Tape	Allocated 15/12/2014 18:02	Overwrite protected until 10/03/2015 05:08

Now because the Friday Full has an overwrite period that ends before the differential, if Backup Exec chooses to use that tape it will invalidate the differential backup tape...

Is there something different I should be doing with this?

I noticed that when using the Dedupe store if you attempt to delete a full backup it also shows you and asks for confirmation to delete any dependent differentials... does BE do something like this with tape too?

Thanks

[Gurvinder]

Tapes use Media Sets. Disk Storage like Dedupe/B2D use DLM wherein you specify retension.

It is recommended that the media set for daily be adjusted so that the full is available for overwriting post the last differential or Incremental has become overwritable.

For Disk Storage , DLM keeps a tab on which Full , diffs or incrementals are tied to and will wait until the last Incremental retension is over.

This is not the case with Tape Media which follow media set rule.

http://www.symantec.com/docs/TECH5459 (you can check this to make changes to media set so that Full is not available for ovewrite until Incremental become overwritabel.

[SSR_7767]

That is not possible with Tape storage.

Just to make sure you do not lose any of your full data before the differential is overwritten, you may move the full tape to "Retired Media Set" which will ensure that the tape is not being picked up for over writing.

But this has to be done manually. There is no option in Backup Exec to track the full and differential backup sets.

[pkh]

It is not a good idea to use the "Retired Media Set" because there is a danger the tape might be accidentally deleted.  It is better to create a new media set with a long OPP and use that.

[Colin_Weaver]

If using a GFS model then typically the overwrite protection for your full backups would be longer that your incrementals and therefore unless you have kept all of your tapes in a vault for a long time you should have overwritten the incremental tapes well before this becomes an issue.

In your case it appears that you have set you differential job overwrite protection to the same as you full - which is not typical for a GFS rotation and has not been designed for (although as Gurvinder tried to explain for disk based backups DLM is now designed for that scenario)

Just to explain a reasonably normal configuration with GFS might be something like

- Daily tapes (for differential or incrementals ) would be kept for 13 days (giving a 2 week rotation of each tape)

- Weekly Tapes (so a full) would be kept for maybe 4 weeks (27 day protection)

- Monthly tapes would be kept for 1 year (364 day protection)

If you implement your overwrite potection based on the above then the differential tapes would have expired and overwritten before the full is.

Bear in mind that whether or not daily backups are full, incremental or differential does not change the idea of GFS. GFS rotations actually define that daily backups are kept for less time than weeklies and weeklies are kept for less time than monthlies etc which yes can open up the potential for a file that has existed for less than one week not being recoverable. GFS is therefore a compromise between keeping backed up data vs the number of costly tapes that might be needed to keep every days backup sets for a long period

To achieve maintaining the daily differentials for the same length of time as the weekly full (so moving out of GFS due to business requirements), you would need to set the weekly overwrite protection to 5-7 days more than your daily differentials are set to (so use two media sets) and set the differential overwrite protection to your designed for retention timings (remembering to subtract 24 hours to cover the length of time jobs take to run.)

Note: If however you are bringing old tapes back from vaults for a restore and not intending to overwrite them and not sure of their overwrite protection status, then best practice would be always slide the physical write protect tabs across on the tapes themselves.