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Differential Backups

felonious_caper
Level 5

I have a dilema.

 

Curretly on one server we run the following backups:

 

1 monthly full backup - kept for a year

1 weekly full backup - kept for 6 months

1 daily differential incremental backup - kept for 6 months

and once a weekend we run another full backup to offsite which is kept for 1 month.

 

 

With our current set up, I feel that it is a waste of tape to keep doing the weekly full back up that we keep for 6 months. That weekly full can be recreated with the monthly, plus all of the incrementals from that week. However, what worries me is the weekly off site tape we only keep for 30 days. If it happens on saturday, and information changed 4 hours before it backed up, this full backup will catch it. but then monday's incremental will only back up changes AFTER that full backup. So in a months time, I'll me missing data that changed on saturday morning because I wont have that full backup anymore, and the incremental from monday will not include it.

 

Is my assumption correct?  What are some ways around this? I know one would be to keep the retention period for the offsite tape at 6 months, but at that point, I'm back where I started with wasting tape.

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Accepted Solutions

revarooo
Level 6
Employee

>> Is my assumption correct?  What are some ways around this? I know one would be to keep the retention period for the offsite tape at 6 months, but at that point, I'm back where I started with wasting tape.

Couple of ways around this. When you run your weekly backup that you keep onsite (for 6 months) duplicate it to another tape (can use SLP or Vault for this), that way you can get rid of your additional weekly (that you offsite) and your backup on Monday will capture whatever has changed since that last full weekly.

Another cruder way which I don't recommend is copy the policy and have a full backup schedule only, that way your incremental on the other policy does not check this policy/schedule backup but its own last full but the 1st method above is way way superior and easier to manage.

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revarooo
Level 6
Employee

>> Is my assumption correct?  What are some ways around this? I know one would be to keep the retention period for the offsite tape at 6 months, but at that point, I'm back where I started with wasting tape.

Couple of ways around this. When you run your weekly backup that you keep onsite (for 6 months) duplicate it to another tape (can use SLP or Vault for this), that way you can get rid of your additional weekly (that you offsite) and your backup on Monday will capture whatever has changed since that last full weekly.

Another cruder way which I don't recommend is copy the policy and have a full backup schedule only, that way your incremental on the other policy does not check this policy/schedule backup but its own last full but the 1st method above is way way superior and easier to manage.

felonious_caper
Level 5

with the method you mentioned first. I still haven't eliminated my weekly full backup for 6 months.

felonious_caper
Level 5

I want to end up with the following:

Monthly full for 1 year

Daily incremental for 6 months

weekly full for 1 month offsited

 

but if I understand you correctly....

 

If policy A has a full and differential backup, the differential back ups will ONLY look at policy A to see when the last full or incremental was done

 

and policy B can run full backups and policy A differential incrementals wont use this as it's last full or incremental backup?

revarooo
Level 6
Employee

That is correct. But if you want a full weekly onsite AND offsite, SLP / Vault duplication is the way to go.

You can alter the retention to 1 month if you need. Just think about when the weekly's expire what you will get from the incrementals and monthlys you are keeping - are they enough for DR recovery if necessary?

felonious_caper
Level 5

Granted more backups are always better. The only difference I'd see is requiring much less tape overall while still providing the same amount of information in it's previous state.  Our space in our robot is limited and we are constantly changing tapes.  I'd like to touch the tapes as least often as possible.

revarooo
Level 6
Employee

Understood, you need to think, if I lost all my files can I get them back. So you take the last incremental and work back incrementals to the last full, will it be available, if you're sure it will (has not expired), then you are good to go.

Also consider someone who's altered a file and wants a copy back from 3 months ago, can you get it back etc. 

Felonious, it seems you know what you are doing from here on. Let the board know if you have any more questions.

TomerG
Level 6
Partner Employee Accredited Certified

I think you are approaching this from the angle of saving tapes, but maybe an approach from the expected SLAs (Service Level Agreements) is better? 

For instance, do your customers (users) expect to be able to restore a file from anytime in the day? I mean, if a user creates a file, then deletes it a few hours later, do they expect to be able to restore the data. Of course with daily backups (incremental or otherwise) you won't get this level of restore-ability. You'd need technology like continuous data protection to get that. 

So, although you are worried about some file that is lost on the Saturday morning (your original post), it could be this is just outside the scope of what you need to provide. Or if it is within the scope, then no way around it, keep the backups for that long. Or change your technology so your using something like deduplication storage to be able to manage many daily incrementals without the use of much disk space, etc.and only keep the tapes (which provide a lower level of recoverability) for long-term storage.

When it comes down to it, it should be the business defining the level or restore-ability, and your job to provide it, or if you can't: complain and ask for more money and technology to be able to provide it. I don't think there is a way around your issue without some other changes.

revarooo
Level 6
Employee

Tomer, great post.

felonious_caper
Level 5

I greatly appreciate everyone's input but the topic has seemed to go off focus.

 

I came into a company who needed someone to manage their already existing backup infustructure. I've been finding ways to make things more effecient but I have not changed much in the way of retention periods.  There is a policy for every schedule and a policy for every client and a policy for every off site tape. It's terrible.  I've done a great deal in terms of condensing policies and schedules, and have cut down the amount of tape handling requireed by a great deal. 

 

My users have already defined what they want and that has already been met.

 

All I'm saying is that I found a way to provide the same exact information with the same exact retention period as before using half the amount of tapes. The only thing standing in my way was the one off site weekly that would "rob" me of a days worth of information since it expires so much sooner than the others.

 

Aparently using a seperate policy for the off siting would answer my question if what was stated is infact true.

revarooo
Level 6
Employee

>> Aparently using a seperate policy for the off siting would answer my question if what was stated is infact true.

It would certainly work, but I still believe SLP/Vault  duplication of your weekly backups is the better option.

 

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

A policy for every schedule?

Not good....

Incrementals and full should be in the same policy.

I agree with Tomer - retention levels should match recovery requirements.
Starting point would be to sit with IT management and server owners to obtain recovery needs from business continuity and legal requirements.

Tapes for offsite can be done via duplication - no need for separate policy.
Duplication can be automated with Vault option or with built-in SLP.