NetBackup Appliance and optimized synthetic full backup

[ehshok]

Hello experts,

I'm looking for answers on the best use of synthetic/optimized synthetic backup/restore using 5240 appliance, and I appreciate your kind help.

I'm planning to have the following setup using 5240 appliance. I'll backup my data to dedup pool at the appliance and then use SLP to dupliate the data to tapes. Here is my settings:

1-Dedup pool at the appliance where optimized synthetic is enabled by default.

2-I'll start a full baseline backup at weekend, and then 5 incrmental backups during the weekday.

3-I'll schedule a synthetic full backup on each of the following weekends.

4-My retention period is 6 months for all full and incremental backups.

I have the following questions and I need your help in answering them:

Q1-I understand optimized synthetic will use metadata and pointers only, so that mean all my synthetic full backups are depending on all the previous synthetic fulls and incrementals. What if one of the incrementals or synthetic fulls in the chain is corrupted, does this mean that all my following synthetic fulls are corrupted? What happen if someone expired one on the incrementals by mistake, what will happen to the following synthetic fulls?

If my understanding is correct, which of the following is a better solution to mitigate the upper risk:-

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A-Is it better to have a full baseline backup after a couple of synthetic backups? Let's say each month to have a full baseline backup and then 3 weekly synthetics?

B-To disable optimized synthetic full on the dedup pool, so sysnthetic full will generate a new full backup physically and not through metdata and pointers(Am I correct?) In such case, I'll loose a lot of storage space and the backup time will be high in comparison to optimized synthetic backup.

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Q2. I want to keep the maximum backups at the appliance while duplicating them to tapes, but my concern what should I do in case the appliance local storage is full and I'm using synthetic fulls for 6 months?

Thank you for your thoughts!!

[ehshk]

Does anyone have any answer for me?

Thanks,

Ehab

[tunix2k]

Hi Ehshok !

For deduplication and opt. synthetic backup you need an appropriate license. Optimized synthetic backup is part of accelerator. (traditional) synthetic backup makes less sence if have a dedup backup target. I think you should read (or read again) netbackup administration part I documentation. Additional explanations you can find here:

https://vox.veritas.com/t5/Netting-Out-NetBackup-Blog/Optimized-Synthetic-Backups-Taking-the-art-and...

http://www.settlersoman.com/netbackup-file-backup-and-restore-optimizations-part-1/

It is essential to understand deduplication and ist additional features. Synthetic backup are old style. Optimized synthetic are doing the same but instead on file level it use deduplication. So they are much more efficient. Best is to keep the pricip in mind and forget schedule/TIR etc of traditional synthetic backup.

You will use accelerator:

Some notes to your statements/questions

1-Dedup pool at the appliance where optimized synthetic is enabled by default:

There is no point to enable/disable opt. syn. backup. Dedup is required for it.

2-I'll start a full baseline backup at weekend, and then 5 incrmental backups during the weekday.

You should enable accelator (policy setting). The first full is like a baseline with less optimization. To have a incremental every weekday is fine.

3-I'll schedule a synthetic full backup on each of the following weekends

Yes, made by a "normal" full backup schedule. opt. synt. backup is done by having accelerator enabled. There is no schedule type optimized syntethic backup. Traditional synthetic backup is file based. 

4-My retention period is 6 months for all full and incremental backups.

Retention periods should reflect your needs. If incremental backups have the same retention like full backups, they will be useless for full restores if the pending full backup is expired. I have often see to have full for example for 6 month and incr. for 3 mounth. This means you are able to perform restores with granularity of one week for 6 month back and with a granularity of 1 day for 3 month back. But on a dedup pool it would not really save space.

Q1 Your understanding is right. I see 2 points where a backup may not correct:

1. wrong reading from client (bit errors etc. which corrupt a file prior to backup and dedup) which is very unlikely or you have disk/filesystem/other i-o error on client os.

2. Journal or track file incorrect: Create a extra full schedule for every month ore every three month with option accelerator forced rescan

If someone expire mistaken an images nothing is happen with your opt. synt. backup except that some dedup fingerprints are not available. I thing the different is not measurable. It is the same if an image expired because of reach its expired period ends.

Q2 If your dedup pool is full you cant write backups to it. Regardless of accelerator or not. To reclaim space you have to expire the oldest images. The amount of space you get back depends on the deduplication ratio, kind of clientdata number of clients .. 

Performing a non accelerator full backup to a dedup pool will create the same backup image like an accelerator backup. The different is that all data are coming from client. You may speedup by using client side dedup. So the needed space for the dedup images and the space for catalog information are similiar.

ciao

tunix2k