Using XSI Backup Pro 1.2.9 and have 2 errors on the backups.
The first is after moving a backup file to a datastore, all the other VM's backup without a problem but this one fails in creating a directory on the target NFS datastore
error: vmkfstools error, details: Failed to clone disk: Not a directory (1310729).
mkdir: can't create directory '/vmfs/volumes/
On another server we have an issue
vmkfstools error, details: Failed to clone disk: The destination file system does not support large files (12).
Other than a disconnect and reconnect of the NFS data store nothing has changed.
You can't create a directory at '/vmfs/volumes/', that is the root of the datastore tree. The ultimate reason why (c)XSIBackup is trying to create a backup at that point can vary. Try to debug your setup, (c)XSIBackup is a script, thus it's easy to set debug points, in any case this will most likely have to do with your VM layout. Check the .vmx file, try to remove any special characters from paths or comments, etc...
In regards to the target volume not supporting large files, I don't know what else we can add to that message. Some file system have a limit in the size of the files they can host. If you try to backup to a FAT32 FS you may not be able to write files bigger than 4 GB per instance.
Format your backup volumes using some file system that can host big files, we strongly recommend: ext4 and XSF