Alex Pankratov :
Apr 11, 2019
This is weird, but the cause is external to bvckup2.
That is, something on your machine (or the remote end if it's an over-the-network backup) is slowing down program's disk access when files are being updated. Any sort of "malware scan" or "antivirus" will likely to be the cause.
There are two relevant differences between creating and updating:
1. The program opens an _existing_ file (obviously)
2. The program actively modifies per-file delta state that stores block
hashes for files copied with delta copying.
The latter can potentially trigger some false positives in "ransomware monitors", because block hashes are ultimately random data that looks exactly like something encrypted. But there were no cases of this sort before *and* it doesn't apply to your case, because smaller files are always copied in full, bypassing the delta copying.
This leaves #1. Something somewhere along the pipeline is throttling down disk access on the backup side. The fact that it's persistently 10 seconds is a red flag. It _is_ some sort of explicit throttling.