Huge difference in data size - production vs. backup

[MSMSMSMSMS]

Hello all,

We have case opened with Veeam for quite some time regarding problem with backup size of our Exchange DAG environment, so I've decided to ask here if anyone else is seeing similar problem. Basically, we have 4 server Exchange 2016 DAG running on Windows Server 2012 R2 based VM. VM's are running on Hyper-V based on Windows Server 2012 R2, and VM disks for databases and logs are formatted with ReFS. We are seeing Active Full Backup sizes that are 2x times bigger than all of data in VM combined. Veeam version is 9.5, but we've seen similar/same behavior with Veeam 9.0. Backup repository is currently formatted with ReFS.

Is there anyone with a similar problem?

Best regards, MSMSMSMSMS

[DGrinev]

Hello MSMSMSMSMS and welcome to the community!

Please, share the case ID number so I could review the details and avoid duplicate questions.

Thanks!

[PTide]

Hi,

Basically, we have 4 server Exchange 2016 DAG running on Windows Server 2012 R2 based VM. VM's are running on Hyper-V based on Windows Server 2012 R2, and VM disks for databases and logs are formatted with ReFS.

I suspect that the reason for such behaviour is that there are dirty blocks that do not contain any data inside the guest. Bitlooker does not work in this case because it supports NTFS only. You can try to zero out free space so it will be deduped during backup.

Thanks

[MSMSMSMSMS]

Hello DGrinev, case ID is # 02042104

[MSMSMSMSMS]

I suspect that the reason for such behaviour is that there are dirty blocks that do not contain any data inside the guest. Bitlooker does not work in this case because it supports NTFS only. You can try to zero out free space so it will be deduped during backup.

Hello PTide,

Your information definitely makes sense. I haven't been aware of NTFS only limitation of that feature. Are there any plans to implement dirty block detection for ReFS?

Best regards, Marinko

[PTide]

Not yet, however as soon as ReFS becomes mature enough we will look into supporting Bitlooker for it.

Thanks