VPS freezes everyday no SSH access.
I have a Ubuntu 16.04 VPS running LEMP (512MB Droplet). This server hosted 3 WordPress sites. Which has 500 daily traffics to 2 sites, other one doesn't have any traffic. All the time RAM usage bellow 300MB and CPU usage also bellow 50% (according to the NewRelic Server monitor)
Problem is everyday after the backup (wordpress backup plugin) run or while running all the sites goes offline and can't connect via SSH (guess server goes offline). All the 3 sites backup are not run at the same time. But digital ocean control panel display that server Up (a green icon in droplet). But if I run CamAV scan, (it use higher memory, CPU than other) there's no such a issue.
To fix this issue every time I have to use Digital Ocean "Power Cycle" option. After that again sites are Up and SSH working.
If I reboot the VPS daily (before the site backup) then there's no such a issue. After that plugin started and completed backup no such a issue.
How do I identify the real reason for this matter? If this is a PHP issue, does it case such unable to connect SSH issue?
*This is NewRelic last 24 hours memory usage (including the this issue occurred time period) *
Click here View Memory Usage Screenshot
Thanks in Advance.