The subject says it all. Trying to upload too big a file stops BT Cloud's upload and then the program goes into a readfile mania. There is no error log. The questions is: how big is too big?
The consensus is 10GB should be OK, though there was never an answer from anyone authoritative. My experience is that the upload process stalls. I had a 12GB file, so I split it with no effect. Ten I moved the big file to a place not to be backed up.
I then got a few more files uploaded, and the upload stalled again. Of course the reporting is so poor I can't tell what has and hasn't been uploaded, and there are no error messages. The remaining files over 1GB are of size (in bytes)
so I moved them to a place where they wouldn't be scheduled for backup and restarted BTCloud. It's chugging away uploading as I type.
It's clear that BT Cloud is not fit for purpose, not least because it a) doesn't say what it has done, and b) you can't AFAIK get a list of what has been uploaded except by laboriously going through each directory. The error handing is just pitiful. How can anyone have confidence that the backup has done what was expected?
Replying to myself: an update.
All the smaller files uploaded overnight. I then moved each of the big files back to where they should live, one by one trying to upload each as it was moved. Mirabile dictu, they all uploaded without stalling BT Cloud. So my hypothesis was wrong, and I no longer know why stalling occurs.
The only large files I maintain for which I would like an offsite backup are system image files, about 30GB in my case. All my early attempts stalled part way but rather than fight it I changed my imaging settings to 2Gb. No failures since and all download tests have been successful.
Continuing my quest to understand exactly what the BT Cloud app can and cannot do I set it to backup a folder containing one file of about 15Gb and a second file of about 8Gb. The smaller file backed up normally but the larger created an error - "you have attempted to upload a file that exceeds the maximum file size of 9.8 Gb" and did not backup. Version 21.2.8