Re: Backing up an external (USB) mounted media on Windows: Incrementals faked?!

I don't think unmount/remount would change the modification time. 
However, it might change the mountpoint. Windows uses a multiple-root 
filesystem. Each drive letter is actually a root path. A remount or 
reboot could very well result in a USB drive previously mounted as E: to 
be remounted as D:. When that happens, Bacula will see all of the files 
as being at a different path than the previous backup, so an incremental 
will be forced to backup the whole drive. Of course it will. If you 
unmount/remount a filesystem on Linux to a different path, Bacula will 
do the same thing.

If that is the issue, then it is also possible to mount the USB drive to 
an empty folder on a NTFS filesystem, rather than a drive letter. This 
can be done in Computer Management/Disk Management using Select Action > 
All Tasks > Change Drive Letter and Paths. The USB drive partition does 
not have to be NTFS, but the folder it is being mounted to does.


On 10/14/24 09:07, Marco Gaiarin wrote:
>> Backup of external media need some specific setup?
> I've changed the subject because was totally misleading; but still i need
> some clue...
>
>
> I need to backup an external, USB, disk mounted on a Win10 client; disk
> contain 8TB of data, scattered in many files/dirs. I'm using progressive
> virtual full, so i'm using 'accurate = yes'.
>
> I've tried with default fileset options, then with 'accurate = sm' but for
> both, sooner or later (i supposed when the client get rebooted; or usb bus
> reset and disk get umounted/remounted) i get an incremental backup of the
> size of a full (8TB), so simply *ALL* files are considered modified by
> bacula.
>
>
> I've tried 'accurate = s5' and incremenetals seems behave right, but an
> incremental took more or less a day to complete. Too slow...
>
> I coud try 'accurate = s' but i think is is unacceptable... too risky...
>
>
> There's some 'knob' to play with? Windows side (eg, prevent to alter/fake
> modification time on remount) or bacula side?
>
>
> Thanks.
>

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