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Backup experts out there , I have question on retention setting for a backup, hope you can explain to me? This is general question, but i am working on UEB

I have a backup schedule full master on Friday and incremental on week days.

I want to keep the backup for 14 days . I assume that i will have two set of masters and rest incremental.

my understanding is that I have to set minimum goal=14 and maximum goal=15.

Hope i am correct on that setting, if not please correct .

I am bit confused in synthesize part.

I read somewhere that that synthesize=minimum goal-max goal -1,

Am i going to get one synthesize here along with 2 master, this case, I will have three master and wasting the storage?

Hope someone will explain this to me.

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Vaira

As far as I am aware, the synthesis function is not going to kick in with your schedule. It is primarily used by the incremental forever jobs in place of the full backups. Since you are already performing your own full backups on a regular basis it would not be needed.

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Vaira - Rob’s answer is spot on. If you need more explanation, I’d encourage you to call our support team. They’re always happy to help partners with their technical questions.

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With Unitrends, the underlying philosophy is to keep as much backup data as possible fur as long as possible. Other than for legal requirements I cannot think of a viable reason for wanting to limit yourself to just two weeks of backups. If you need to keep a minimum of two weeks worth of backup then yes you should set the retention to 14 or 15 days. That threshold is just there as a warning, if it drops below that number then the appliance will warn you.

The maximum retention limit is more for guidance when it comes time for the appliance to purge old backups to make space for new ones. This only happens when the appliance is full and needs to make space. Say you have 5 servers. One you need to keep backups for a year, the rest you only need to keep for a month. You would set the first one to max age of 365 days, the rest to 30. It will continue to back up and keep all the old backups for as long as possible. Say after 200 days the appliance is full and needs to make space, it will not touch old backups from the first server since it is not yet at its maximum retention limit. It will instead delete the oldest backups from the other servers because they are over their 30 days of required retention.

I hope that helps.

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And a few more details from our support team:

To get your end goal, you will need to set a minimum 7 days and a maximum 14 days for retention. This will make your system kick off a synthetic master once a week, and will keep your retention between these two time periods. If you need to hold it for a minimum of 2 weeks, then you will need to set min 14, max 21 to get the same result, but with the retention holding between 2 & 3 weeks.

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I personally believe that the only setting that really matters is Legal Hold. That’s the only way to make sure the appliance doesn’t delete a backup you don’t want deleted.

I leave minimum at 0, set legal hold to the number of days I need to be able to go back, and set maximum to some number higher than that (it forces you to use a number higher than your legal hold setting).

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Great postings. If i Understood correctly the synthesize take place in incremental forever backup if we setup the minimum and max goal , that is 7 and 14 days then there will be one full backup at very 7 days otherwise it will go with one full at the beginning and incremental forever?

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I too am a little confused with the best way to go for retention/archiving. We have a large number of Hyper-V and VMware VM´s, and have been recommended to use the incremental forever strategy. That said, it´s very important that a certain number of days backups are kept on the appliance.

Reading the KB article about auto synthesis, with incremental forever - it will at some point (around 2 weeks approximately, but it depends on many factors) roll all incrementals into a new full. This caught me out, as I had backups running for approx 30 days (it was a new appliance), and needed to restore a VM from 22 days ago exactly. However, when going to restore - I could only see 6 days of backup retention. Even if I had quite some space left on the appliance.

This means, that I even if I set a minimum retention - that does´t mean I will be able to go back 22 days exactly, for example to get restore a specific incremental. As minimum retention does´t really guarantee anything.

Archiving has been suggested, and I could of course archive every week or two weeks. However, then I think I will end up with just two weeks (approx) of data on the appliance due to auto synthesis constantly running (when I know it could hold at least 30 days of incrementals) and a huge amount of archive data on the archive storage. This feels like I´m underutilising the available appliance storage and the possibility of quicker restores for a longer history of data.

So legal hold does seem to make sense for the forward incremental strategy, when you really want to trust that you will be able to restore data on the appliance, from a specific incremental - from X days ago.

Or am I understanding this completely wrong here ?:slight_smile:

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Evan - Thanks for using Unitrends, and our apologies on the confusion that the retention settings may have caused you. If 30 days is your absolute minimum days of retention that you’d like to have on the local appliance, then your minimum setting should be 30, or even better, 31 days. Legal hold is an extra step to ensure that these retention settings are maintained.

In terms of the synthetic fulls, there is an algorithm that the appliance performs to determine when it needs to create a new synthetic full based on retention settings, backup sizes, and frequency of backups. This means that your synthetic fulls may happen once a week, while your neighbors may happen twice a week, since your environments are different.

If you’d like help setting up your retention settings to ensure that you’re meeting your retention requirements, I would contact our support team.

Please let me know what questions you may have about this.

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Thank you Katie. What I think would be a suggestion for Support is - that when they advise customers to use incremental forever (which they generally always push), that they may not be able to trust how far they can go back for restores sitting on the appliance. Even setting a minimum retention doesn’t guarantee this. As you say, it’s the algorithm that works it out… and may be one week, or may be three weeks.

So being warned about this, is quite an important thing in my view - when being advised to use incremental forever. At least for customers who are in the implementation phase…

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Again…why I said earlier in this thread that Legal Hold is the only setting that really matters.

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I think the minimum and max goals are not gurantee unless you set legal hold for 7 or 14 days etc.

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Evan - Thanks for this feedback. I’ve shared it with our support, development, and installation teams since this is definitely an issue that we need to tackle.