I run a few different client sites on a WordPress Multisite hosted on a 'premium' dedicated VPS server on Bluehost. This has been working very well for me.
One of my clients sites, rubygettinger.net, is very popular. She will often link to her site from Facebook. At times the site will get a good amount of traffic and she will notify me that she is getting the "Error establishing DB connection".
To solve this problem I upgraded my server on Bluehost when this was first happening and it seemed to fix it. I recently put a forum on the site and when she shared it yesterday she started hearing from users who were getting the error.
I was not notified that the site was down at all (via pingdom, new relic, or the wordpress monitor from jetpack).
I'm self taught so any advice is much appreciated! Please let me know if I'm doing something totally wrong here or how I can prevent this error.
I am considering using the WPMU Multi DB plugin.