PBS Tape Backup, understanding options for retention and allocation policy

[Jackobli]

Hey there

We are using pbs for some time to our full satisfaction.
Some weeks ago we ordered a small tape autoloader and began to do offline backups.
(1 drive, 8 slots, 3 marked as export slots).
We were really happy how good and easy the setup of the autoloader was, congrats to the team.

Actually we (or me) are a bit confused with the options and allocation policy.
Although reading the manuals, the system did not behave as (most probably wrong) expected.

What we would like to achieve:

1. Do a weekly new full backup (Friday, 22:30h, runs around 33 hours) and export the (two) tape cartridges after
2. Use a new tape to do a daily backup of last changes for Sunday to thursday and then export the (one) tape after
3. After four weeks begin to reuse the oldest tapes

The full backup was ok, but doing the daily with a new pool ended in starting a full backup again (what makes sense afterwards).
So we tried to use the same pool, but the next friday it did *not* run a full backup.

So maybe we need to use four (or five) separate media pools? Or how could we arrive to do, what we would like?

We got the support contract, but this seems IMHO a question others might find interesting, so public here in the forum.

Regards, Urs

 

[dcsapak]

mhmm without testing what should work i think is the following:

have single media pool X

allocation policy: friday sometimes before 22:30 e.g. 20:00
retention policy: 3 weeks (or depending on timing may be better to use 20 days)

one backup job at friday 22:30 , + export
one backup job for the daily backups

that should create a new media-set on friday 22:30 job (always) and reuse it for the following days until the next friday
did i understand you correctly?

 

[mow]

that should create a new media-set on friday 22:30 job (always) and reuse it for the following days until the next friday
did i understand you correctly?

Does that, after the export, automatically allocate another tape for the daily incrementals?

 

[dcsapak]

Does that, after the export, automatically allocate another tape for the daily incrementals?

mhmm... actually reading the docs, it may allocate a new media-set if the required one is missing, but what you could do is to set the 'writable' tape to status 'full' either manually or via api/cli that would mark the recent one full and a new tape would be requested

 

[Jackobli]

mhmm without testing what should work i think is the following:

have single media pool X

allocation policy: friday sometimes before 22:30 e.g. 20:00
retention policy: 3 weeks (or depending on timing may be better to use 20 days)

one backup job at friday 22:30 , + export
one backup job for the daily backups

that should create a new media-set on friday 22:30 job (always) and reuse it for the following days until the next friday
did i understand you correctly?

ok, we have a single media pool (or one test pool and one prod)
I see, allocation policy is the keyword we're have to look into.
According to the manual, this should work:

• Create a new set when the specified Calendar Event triggers.

I will try starting from this Friday and than report.

 

[Jackobli]

Does that, after the export, automatically allocate another tape for the daily incrementals?

Yes, this did work for us. If exported (not only ejected), that autoloader does not try to get the media back and started with a new tape cartridge.

 

[Jackobli]

Thank you again for the support

Now, everything works as expected.
Our settings:

• Media pool: Allocation friday 20:00h
• backup jobs:
  • 100: Eject = No, Export = Yes, Latest only = No, Schedule = Fri 22:30
  • 200: Eject = Yes, Export = No, Latest only = Yes, Schedule Sun - Wed 22:30
  • 201: Eject = No, Export = Yes, Latest only = Yes, Schedule = Thu 22:30

Thus, we create a full backup on friday til sunday (needs more than 1 day) and export the cartridges to store it outside. The daily diff get's exported on thursday. With this setup, the Autoloader needs few attention after weekend to get the exported cartridges out of it and to fill in new cartridges.

regards, Urs