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What data is kept in a long running backup?

  • 6 January 2022
  • 7 replies
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Let us say you have a backup that for various reasons stretches over three days.

We have days 1, 2 and 3.

Backup “window” is from 1700 hours to next day at 0800 hours.

Backup starts day 1 at 1700 hours end on day 3 at 0800 hours.

During work hours on day 2 and 3 files are changed, deleted and replaced on the server we are backing up.

What data will be in the backup when finished on day 3?

Will data from day 2 and 3 be there or does CommVault make a delta snapshot file on day 1 that contains the data that will be backed up?

Steeler

 

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Best answer by Dan White 7 January 2022, 16:55

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dude
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Well, it depends.

How is the backup configured? Are you taking snapshots I assume based on your comment? Can you describe a little more the environment?

Mike Struening RETIRED
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@Steeler , I’m going to assume you are referring to non-snapshot agents (though @dude ‘s question is valid).

Whatever the scan process ‘sees’ and adds to the collect file will be backed up, no matter how long the backup phase takes.

Before the backup phase, we scan the content in the subclient, list out what needs to be protected (let’s assume normal files here), then once the scan finishes, the backup phase will grab those scanned files (from the collect files) and back them up.

If any file in the collect list is deleted between scan and backup, it will be skipped (unless vss or some similar function is able to cover).

The next time an Incremental runs, any files that changed during the backup will be seen as new, and added to the collect file to get backed up.

Now, there are some instances (snapshots, aux copies) where this is not entirely accurate, but it is a good baseline experience expectation.

https://www.linkedin.com/in/michael-struening
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Thank you for your answers.

@dude  - we do VM snapshots and agent based file backups over a wide range of customers.

I know my questions are very basic but no one has ever explained to me what steps go into a backup.
For reporting purposes, I need to know which days a backup has completed successfully and which has not. It is not as clear cut as it may seem as we experience days with long running backups as in the example.

Steeler

Mike Struening RETIRED
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If the backup is based on the snapshot, then I would expect us to have everything from that snapshot’s moment in time in the backup.

I’ll add in some people to get a confirmation.

https://www.linkedin.com/in/michael-struening
Aplynx
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When using VMware, CommVault relies on VMware’s CBT or in some cases CRC to capture any changes in the snapshot. Then the snapshot is backed up. 

File system backs up what is captured during the scan phase using Change Journal to record changes in folders\files.

In both cases the scan or snapshot phase designates what is backed up and the backup phase records those changes.

Liam
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@Aplynx  Same concept would apply here, yes!

It doesn’t directly answer the question but certainly helps in understanding

https://kb.vmware.com/s/article/1015180

"If you give a man a fish, you feed him for a day. If you teach a man to fish, they will probably burn your spot"
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Thank you for your help…..

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