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How often do I need a full backup?

Post by dstreufe » Oct 03, 2011 11:59 pm

I see that the FAQ says this is possible, but what is the best practice around how often I need to take a full backup? Due to the type of storage I am using a synthetic full takes a LONG time, and an actual full takes about 35 hours. Instead of doing this once per week, I would like to do it once per month or less.

How far apart can I stretch the interval between full backups before I am flirting with trouble?

Thanks,
Dan

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Re: How often do I need a full backup?

Post by Gostev » Oct 04, 2011 9:45 am

Hi Dan, recommended values are as follows:

For incremental backup mode:
• Synthetic full weekly (UI will not allow you to schedule synthetic less often for performance reasons), OR
• Active full monthly (driven primarily by retention policy and disk space considerations - unlike with reversed incremental backup, older restore points cannot be deleted immediately, until the new full backup is created)

For reversed incremental backup mode:
• Active full once every 1-3 months (this backup mode is specifically designed for long incremental chains, but Active Full is still good for the purpose of defragmenting and reducing full backup size).

That's what I am seeing other customers doing typically. Internally at Veeam are not using active fulls at all, but effectively they still happen once every half-year or so because of various job re-arrangements, Veeam B&R upgrades etc.

Thanks!

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Re: How often do I need a full backup?

Post by 1-0-1 » Oct 04, 2011 5:57 pm

What happens if the incremental backup chain is broken. Do I just loose that point in time backup or loose the whole chain from the faulty incremental?

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Re: How often do I need a full backup?

Post by Gostev » Oct 04, 2011 6:59 pm

The latter, of course. "That point only" would require differential backup to be performed, which is not reasonable on image level (backup time and size considerations).

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Re: How often do I need a full backup?

Post by dstreufe » Oct 04, 2011 7:22 pm

Gostev,

Thanks for the info. We will go with monthly active fulls. If we had plenty of disk space to, say, go with a longer interval such as quarterly, would there be other reasons to avoid this?

Thanks,
--Dan

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Re: How often do I need a full backup?

Post by tsightler » Oct 04, 2011 7:37 pm

Honestly, performance starts to be noticeably worse with very long incremental chains. Importing a long incremental chain takes MUCH longer than a short one, and the dead time (the time between when you start a restore and when the transfer of data actually starts) also increases quite significantly. Because of this, I always suggest at least monthly fulls if using an incremental policy. This also helps mitigate the likelyhood of a single bad incremental file causing you to loose weeks, or even months, of backups.

These issues are less noticeable for reverse incremental. Even very long chains seem to have only minimal performance impact. I think this has something to do with the way metadata is stored as, with forward incremental, each file has to be read to process the metadata (previous files are never touched), while, for reverse incremental the most recent VBK contains all of the required metadata. V6 will likely minimize this issue as there are significant changes to metadata handling coming with V6.

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Re: How often do I need a full backup?

Post by Daveyd » Oct 05, 2011 7:18 pm

tsightler wrote:Honestly, performance starts to be noticeably worse with very long incremental chains. Importing a long incremental chain takes MUCH longer than a short one, and the dead time (the time between when you start a restore and when the transfer of data actually starts) also increases quite significantly. Because of this, I always suggest at least monthly fulls if using an incremental policy. This also helps mitigate the likelyhood of a single bad incremental file causing you to loose weeks, or even months, of backups.

These issues are less noticeable for reverse incremental. Even very long chains seem to have only minimal performance impact. I think this has something to do with the way metadata is stored as, with forward incremental, each file has to be read to process the metadata (previous files are never touched), while, for reverse incremental the most recent VBK contains all of the required metadata. V6 will likely minimize this issue as there are significant changes to metadata handling coming with V6.
If you are only doing monthly fulls, how many rollbacks do you keep?

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Re: How often do I need a full backup?

Post by tsightler » Oct 05, 2011 8:10 pm

We had various servers that required various retention periods. We tailored our backups jobs to use the mode that provided a balance between space, retention, and performance. For example, for servers that had fairly low changes rates and long (180 day) retention requirements, we just used reverse incrementals.

However, we had quite a few servers that had 90 day retention of daily backups, and multi-year retention for monthly backups. These servers also had a moderate change rate. Monthly "real" fulls were perfect for this case. We archived the monthly's to tape for the long term retention requirements and had 90 days online.

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Re: How often do I need a full backup?

Post by brupnick » Oct 11, 2011 1:29 pm

If I'm doing traditional incrementals on week days (M-F) with active fulls on say the first of the month and I want to keep 2 months worth of restore points (call it 40, 20 points per month), does this mean that I'll need enough space to keep 3 full backups? Based on Gostev's comment that "older restore points cannot be deleted immediately, until the new full backup is created," the first full will also be the 41st restore point, meaning that it will be the first file targeted to roll off. But since that full is needed for all of the subsequent incrementals for that month, am I correct that it cannot be deleted until all of the incrementals that rely on it also exceed the retention period (or a new full is run manually)?

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Re: How often do I need a full backup?

Post by foggy » Oct 11, 2011 1:37 pm

Yes, that's correct. You will need enough space to store 3 full backups.

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Re: How often do I need a full backup?

Post by davidb1234 » Dec 01, 2011 2:56 pm

If the option to transform all previous full backup chains to a reversed incremental backup sequence is chosen will that eliminate the need to store 3 full backups in Brupnick's case(since his question also applies to me, we want to do forward incremental and hold 3 months of data but we would rather only keep one full backup on disk and have 3 months worth of reverse incrementals.) We need forward incremental so we can offload to tape nightly but would like to transform these to reverse incremental after synthetic fulls so we don't have to keep so many fulls on disk and can store more data.

In this case would we also be able to go back to a vm point in time and recreate a full VM in the past from the most current synthetic full and the transformed reverse incremental backup chain?

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Re: How often do I need a full backup?

Post by foggy » Dec 02, 2011 9:37 am

Yes, correct. With transformation into rollbacks you will always have one VBK file stored and will be able to restore to any restore point kept according to your retention policy.

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Re: How often do I need a full backup?

Post by Daveyd » Dec 02, 2011 4:29 pm

I have several jobs that I have configured to keep 7 restore points and do weekly fulls on Saturday with daily incrementals M-F. Looking at my destination storage, my chain look like this...

Full
Inc
Inc
Inc
Inc
Inc
Inc
Full
Inc
Inc
Inc
Inc
Inc
Inc

So basically 6 incrementials per Full. If I decided to keep the 7 restore points the same and change to Monthly Fulls, what would my chain look like?

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Re: How often do I need a full backup?

Post by dstamen » Dec 02, 2011 4:42 pm

We are currently doing daily incrementals with a synthetic full once a week transforming the previous full into rollbacks.

Which seems like a better solution?

Inc
Inc
Inc
Inc
Inc
Inc
Inc+transform previous full

or should we go
Full
Inc
Inc
Inc
Inc
Inc
Inc
Full

what has worked out best for most of you?

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Re: How often do I need a full backup?

Post by foggy » Dec 02, 2011 4:51 pm

Daveyd, you will have somewhat from 6 to 34 (or 35, depending on the month) incrementals and 1 or 2 fulls. Here is a couple of threads with good explanations of the incremental mode: one and two.

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