FTP backlog memory corruption

rho

I have a number of camera's set up to FTP files to a server and are also fitted with SD cards.
I recently encountered problems with the SD card either being exceptionally slow to update (several minutes) or in two cases loose an entire days recordings. At first I thought this was an ageing problem of the SD cards but I eventually traced it to buffer overflow within the camera due to FTP backlog.

I had the ftp postpone set to 30 seconds but discovered due to a temporary slowdown in the server (due to a slow SSD) the resulting file was taking a lot longer than 30 seconds to transfer so if there were frequent alarms the camera would build up a backlog and eventually become corrupt.

The very slow SD writing manifests itself when an alert is received it is found the corresponding SD recording is very short (typically showing 40secs or less and corrupt in that replay fails, however several minutes later when the ftp transfers are complete the recording is suddenly updated to it's true length (several minutes) and playback becomes possible.

So it seems Reolink have a classic buffer management problem and SD recordings are not closed/completed till the ftp transfers are complete!

I have for the time being increased ftp postpone to 1 minute that alleviates the problem. I hope the problem goes away once I increase the speed of the ftp server but I hope my description helps others with mystery disappearing recordings and slow SD problems, if in doubt switch of ftp!