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Chihiro
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Incremental Backup Mechanism

Post by Chihiro »

I am using Veeam Backup 3.1 on Windows XP to back-up from a ESX 3i host; over the LAN and non-VCB. I am not staging backups at the moment, so all my full and incremental backup files are stored in a single target directory. In the future, I'd like to perform staging (i.e. move each sessions' backup files to secondary/removable storage), in which case incremental jobs would not have the original full or previous incremental backup files to "refer" to. I'm half-assuming Veeam Backup stores session data in SQL so it wouldn't need previous backup files, but... I have noticed that after performing an incremental backup, the timestamp for the original full backup vbk file and previous incremental vbr file(s) gets modified. It might just be me (or my XP environment) but I wanted to ask if anyone else has noticed this.

I guess my question is: For a given job, must the previous backup files (full and/or incremental) reside in the working target directory for subsequent incrementals to be successful?

And for extra credit: If the full backup file doesn't need to be available for incrementals to succeed, how does Veeam Backup know what changed in a VM? Since it's not a file-based backup, I'm almost certain it's not using OS-level archive bits or timestamps...

Note: I do realize that for restores, the original full backup plus incremental backups up to the restore point are required.

McClane
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Re: Incremental Backup Mechanism

Post by McClane »

Veeam Backup does virtual full backups. The *.vbk files are the up to date full backup files. The *.vbr files are the incremental data as difference to the full backup. Thats why the vbk is updated after every backup.

Chihiro
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Re: Incremental Backup Mechanism

Post by Chihiro »

Thanks for the reply, McClane, but I still don't understand. If the *.vbr files are the incremental data as difference to the full backup, then there should be no reason for the vbk (full backup) files (or previous vbr files) to be updated/modified when incremental backups are run, right?

When I run an incremental backup using ARCserve/BE, it doesn't ask me to insert the tape containing the first full backup or previous incremental backups.

Can a Product Manager please reply? My company is considering purchasing this software if/when we fully understand its capabilities/limitations.

pizang
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Re: Incremental Backup Mechanism

Post by pizang »

RTFM. What differentiate veeam from other backup software is how it manages full backups. You are making an incremental backup but in a result you got full backup. Magic :). Veeam can calculate from your yesterday's full backup and today's incremental backup a today's full backup and yesterday backincremental backup. So yesterday's backup consists of changes that where made since today. If you will take today's backup and revert changes (written in yesterday backincremental backup) you will have yestarday's state. That is why system is changes dates for 2 files.

Please read the manual. I think it is written more clearly I guess.

Vitaliy S.
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Re: Incremental Backup Mechanism

Post by Vitaliy S. »

Hello Chihiro,

Yes, for a given job all files (VBK and VRB) should reside in the working target directory so that retention policy is successfully applied and you have a correct chain of rollbacks, cause when every incremental run is made, all the data is inserted to your VBK file, and previous rollback are pushed out to a new VRB file (the way how synthetic way of backup works).

Regarding your second question, Veeam Backup and Replication traces all changed blocks in your VM and operates with these blocks only during an incremental run.

As for your question with dates modified please have a look at the following topic, I believe it'll answer your question concerning dates changing:
http://www.veeam.com/forums/viewtopic.php?f=2&t=1479

Chihiro
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Re: Incremental Backup Mechanism

Post by Chihiro »

vsafarov,

Thanks for your reply. Everything is much clearer now. I did read the User Guide before installing your software, but I guess I misunderstood the sentence Obtained changes are backed up and saved as a service .vrb file next to the full backup .vbk file. on page seven (under Synthetic Backup). This sounded a bit like a traditional full+incremental backup framework. I'm new to synthetic backups, but I understand it now after reading around.

I'm just reassuring myself here, so please feel free to reply only if I'm mistaken: Basically, for each session (except the first), the .vbk file is updated and a new .vrb file (most previous rollback) is created; all the while other/older .vbr files are left alone (or deleted as per the retention policy).

P.S. This article was very informative: http://veeammeup.com/2008/08/veeam-synt ... ained.html

Gostev
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Re: Incremental Backup Mechanism

Post by Gostev »

That is correct.

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