I use VPS (2GB RAM 40GB SSD Disk). There are about 80 sites Drupal running on VPS mine. Recently, VPS My frequent loss of connections MySQL, and VPS deactivated. I often have to Power Off and Power On to make it work again. I think VPS is overloaded, because there are so many sites running (around ~ 100 view / day / website). Do I need to upgrade VPS?
8000 daily viewers should not be an issue for a 2GB droplet but this will depend on your site(s) configuration and resource use. What messages are you seeing in the MySQL log file in /var/log/? The log should provide more detail about what is occurring and will give us a starting point to resolve it.
Look at your memory consumption (free -h) and CPU loading (command top, check the value of loading average, if it's more than ~2 your CPU is highly loaded). Also, make sure you have enough disk space (df -h).
As a way to improve overall performance you can use Varnish cache as a reverse proxy for all of your website, but this would help only with anonymous traffic.