Following this path I think nothing will come around…
So.
Thanks for the log, but without a more detailed explanation of your installation, the way you’re trying to backup your server and what is the target (NAS, Linux Server, Windows Server, SFTP site, cloud service, whatever) there will be no chance guessing why the attempts got “IOError” instead of something better.
If your server is connected to a subscription, maybe opening a ticket could be an option interesting enough for you.
Anyway…
Procedure start with data preparation for the backup
Backup started at 2021-04-20 01:00:01
Pre backup scripts status: SUCCESS
But obviously something is going in the wrong way; the only glimpse of what’s wrong is related to this part of the log No valid VFSType: UNKNOWN
Also… due to the procedure for create a data backup procedure, the destination has been validated, (somedate, sometime) by the backup module.
Therefore: maybe at that time the destination was shut off, unavailable (change of access rules due to time restrictions or time condition firewall rules) or… destroyed? Who knows…
More info, more way to try to help you.
This question without any info is useless for who reads…