I want one disk in my NAS (currently deciding between DuoV2 and NV+V2 - would probably buy an Ultra if it had USB3.0 Ports) to be dedicated for TimeMachine backups for my two Mac notebooks. AFAIK you have to choose the max. size of that backup, since TimeMachine will make a virtual partition which for the Mac will host an HFS+ volume, but for the NAS it will just be one big file located on its Ext4 formatted disk, right?
Does this mean, every time I first run a TimeMachine backup from my Mac it will e.g. transfer 3 new files with a total of 1MB data to the NAS, and then would want to backup the NAS drive to an external USB drive connected to the NAS, then the whole big file (e.g 1TB) with the virtual partition needs to be transfered to the USB disk? Of course it needs to be transfered once, but I am talking about incremental updates.
Or does the NAS know that the last TM run only changed less than 1MB, and so only needs to transfer that changed 1MB to the external USB drive?
for the NAS it will just be one big file located on its Ext4 formatted disk, right?
No - the target is a sparsebundle disk image which, while appearing as a single disk image to Time Machine is in fact a data structure consisting of multiple smaller files (IIRC 8MB blocks)
Try creating one on your Mac using disk Utility, and explore it to see how the image is built.
fesh wrote:
Or does the NAS know that the last TM run only changed less than 1MB, and so only needs to transfer that changed 1MB to the external USB drive?
All backups are incremental (except the first) - only data changes are backed up.
