Like many people, I have a Synology NAS that I use for backups. I backed up various Windows Servers to a Share on this NAS overnight using tools including Veeam, but it kept failing but only intermittently. Yes, I know; the worst type of error is an intermittent error.
Each time I ran the backups manually, they seemed to run fine. That was until they didn’t run, and I received the same error. Eventually, after looking through the Event Logs, it appeared to be an SMB failure. Armed with this additional, missing piece of information, I was able to determine that the problem was a simple timeout problem – the disks in the Synology system are just spinning rust, and the network connection in it is only 1Gb – and with the large amount of data being backed up each time, it was timing out.
The fix was surprisingly simple. On the Veeam Windows Backup server, I issued the following command in Powershell as an Administrator, and the problem vanished. The server has now been running for weeks without a hitch.
Set-SmbClientConfiguration -SessionTimeout 600
