CobianSoft

Cobian Reflector creates a zero-size archive after copying to the NAS (Synology).
However, the archive is not zero length in the working directory on the local disk before copying.
I am creating a global monolithic archive.

If you disable the compression, does it run OK then?

Yes, then it run OK.
In the previous version (Backup 11 Gravity) I have no problem with practically the same backup settings. The difference here is only in the choice of compression program 7zip, which is not in the new version. The resulting archives are over 100 GB in size.

In this version the archive is created in the temporary directory first, then copied to the destination. Do you have enough space at the local drive?

There is enough space on the disk where the temporary archive is stored, and the archive will be created correctly, including the archive check. Then the file starts copying to the NAS, the file grows quite normally, but after 100% completion, the archive becomes unreadable (corrupted) with zero size.

So the problem is not with compression but with the copy... Is the NAS Ext3 formatted? The maximum file size for ext2/ext3 is actually dependent on the choice of blocksize and hardware architecture. Sometimes the limit is just 2 GB

As I wrote earlier in the previous version of Backup 11 Gravity, the backup works for me on the same NAS without problems and I also make archives larger than 120GB (with the difference using 7z archiving).

Really no idea then. Another theory is that some antivirusprogram is working checking the archive on the background. Few antivirus check 7z archives but some of them lock and check zip files.