CBT with B&R backup & replication

[itdirector]

B&R 6.1 - vSphere 5

If we run a replication at 12:30PM everyday & a backup at 1AM every morning, both using CBT, does each job reset CBT? As in, if we run replication at 12:30PM on Monday, & backup at 1AM on Tuesday morning, then replication again at 12:30PM Tuesday, will the 12:30PM tuesday replication job using CBT transfer all blocks changed since 12:30PM Monday, or has the CBT reset & it will only replicate changes from 1AM tuesday morning?
Obviously, we would like all changes since last replication for that specific 12:30PM job (since we also do replication to our DR site using another job).
Thx

[bgbGsy]

Hi There. If you want a good indept explanation of how VMWare does Snapshots with CBT, take a look at the http://www.vmware.com/support/developer/vddk/

Basically, it handles the situation you described.

All the best.

[Vitaliy S.]

...and here is another topic to take a look: VMware : [FAQ] FREQUENTLY ASKED QUESTIONS

[dcs115]

I just started doing remote backups that are retained for 5 weeks. I have a separate job that runs a on the same set of VM's, but to a local repository that are retained for 1 week. Everything runs as reverse incremental.

My question is that when i started running two jobs on the same VM's, my incrementals started to get really small. This made me think that when Job A (local repository) runs, it only copies the deltas from when the last job ended and job A starts, but when Job B (remote repository) runs it *only* copies the deltas from when Job A ended and B began. This would of course mean that the backups are not "complete" for the purpose of restores. Is this the case? Is there anyway to mitigate it? Perhaps by turning of CBT? Would turning off CBT defeat the purpose of incrementals?

To put it another way, what does B&R look at when it runs an incremental. Is it CBT or does B&R compare the chain of backups and only grab the deltas in the newest incrementals.

It is my understanding that if you want a local and remote copy of backups, the best ways is to run 2 separate jobs.

Thanks!

[dcs115]

This may not be the correct forum for this, but since everything that is taking two backups of the same VM's is doing it, it is probably worth noting.

It is my understanding of Exchange that if you have two backup jobs running, where both are taking incrementals, and then Job A takes a full backup, while Job B keeps taking incrementals, all of the incrementals that Job B takes are no longer usable because Job A has removed the transaction logs that Job B would need to restore back to its full.

I thought I could get around this by taking full’s on the same day, but after i thought about it, I believe that whichever job takes its full backup first, will have its subsequent incrementals rendered useless by the full backup that is taken by the job that runs next.

If all of this is correct, then only way to have a local and remote backup of your Exchange server would be to take a weekly full at one location (no incrementals at all) and at your other location take a full backup (only after the site with no incrementals has finished its full backup), then start taking incrementals and repeat weekly.

It would be very convenient to be able to have one job pipe backups to two repositories .

[Vitaliy S.]

Hi David,

To put it another way, what does B&R look at when it runs an incremental. Is it CBT or does B&R compare the chain of backups and only grab the deltas in the newest incrementals.

CBT is tracked on per job basis, so having multiple job backing up the same VM, does not affect other jobs.

It is my understanding of Exchange that if you have two backup jobs running, where both are taking incrementals, and then Job A takes a full backup, while Job B keeps taking incrementals, all of the incrementals that Job B takes are no longer usable because Job A has removed the transaction logs that Job B would need to restore back to its full.

It does not matter whether you run full or incremental job pass in this case, as SQL transaction logs are truncated in the same manner for every job run (provided that you have "truncate logs on successful backup" option enabled for your backup jobs), so both your backups are valid.

Thanks!

[bmwisme]

Ok, I spent an hour reading various threads and think I have a handle on this but no where did I find an explanation on how/why this works. The issue is CBT and multiple jobs running against the same VMs.

I have my primary daily incrementals with weekly synthetics fulls to local storage (local proxy, local repository). I then run periodic backups remotely via a remote proxy to its own local repository. I have read that this should work fine and there are no CBT issues. I guess I don't need to fully understand why it works but I am curious. One could assume that CBT is similar to archive bit functionality but I am curious how this works with multiple jobs for the same VM. Does each Veeam job work independently with CBT - any one job not resetting what was/needs backing up?

Sorry, I am sure this has been covered before but there is only so much time in a day for an admin to study each new product and uncover all functionality.

Thanks,

Bill

[dellock6]

CBT does not work as an archive bit, think of it more as a log of changed block, each with its position and timestamp. When a software reads CBT informations, it searches for a desired timestamp (in Veeam is the time of its previous execution), and read which blocks have changed since then.
Another software (could be two different backup jobs) can read the same log and search for another timestamp. That's why it can support several backups without any interference.

Luca.

[bmwisme]

Thanks Luca, very good explanation and to the point.

[Harry-V]

Hello to all,
I want to assure alternating 2 different repositories with reversed incremental. First job Monday-Wednesday-Friday-Sunday, second job Tuesday-Thursday-Saturday. Is that even possible with CBT? Probably not. This works but maybe if CBT is disabled? Any ideas?
Thank you.

Greetings from Germany

[Harry-V]

Hello to all,
I want to assure alternating 2 different repositories with reversed incremental. First job Monday-Wednesday-Friday-Sunday, second job Tuesday-Thursday-Saturday. Is that even possible with CBT? Probably not. This works but maybe if CBT is disabled? Any ideas?
Thank you.

Greetings from Germany

I think this is answered by Luca ...

[marius roma]

A job backs up a group of VMs every night and works fine.
During a server farm maintenance activity I need to create a new job to backup a given VM (included by the previous job) for three days at noon.
It will be a separate job (and I presume that I will have a separate backup on the NAS).
So I will have 2 backups of the same VM, one made during the night and a different one made at noon.
Can the noon backup disrupt in any way the normal backup made during the night?
Should the noon backup be configured in any specific way?
Regards
marius