Does CBT = Disk writes

[tdc-ma]

Maybe little off topic just wondering would CBT incremental (uncompressed) backup size equal or close to equal to how much data was actually written by the vm in that period.

Thinking of ssds and wondering how much VMs are writing all the time and little that I did look how to gather that I can't find a reliable way yet

I'm playing with this in my home lab and I am also fully aware what SSD write amplification is and that even if CBT backup equals the writes to a byte it won't equal actual NAND writes

Thanks

[EugeneK]

CBT is not necessarily writes only, it's the changed blocks in general - can be added/removed/updated/modified blocks.

[foggy]

Besides, even if only 1KB of data has changed inside the VM, the entire block containing this change will be copied by Veeam B&R (block size depends on the storage optimization settings and varies from 256KB to 8MB).

[Anders]

If one block is changed a thousand times it will only be listed as changed in CBT- so that alone would make it useless to calculate how much data is written.

VMWare performance Graphs might give you a better answer. (If the VM have an average of xx KB/s writes over 24 hours, it would be easy to calculate the total amount of KB written)

[PTide]

Hi,

In case you backup a VM with Windows as guest OS and NTFS filesystem then you' might be interested in BitLooker - a feature that allows you to exclude files that has been deleted so you backup only data that not only has changed but also is still present on a filesystem level.

Thank you.