How to tweak Mysql open_files_limit and table_open_cache to avoid dB crash?

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Hi, I recently merged three dedicated server into one, i have 50 websites, and unexpectedly, mysql has difficulty to work well.

I followed the post here to increase the ulimit https://duntuk.com/how-raise-ulimit-open-files-and-mysql-openfileslimit
I set 102400 (while the post said a higher value)

I noticed after two days,mySQL server may start to have problems. I could add two zeros to the limit, but will it be sufficient?
The command : show global status; returned a value of 160K for the opened_files, 786 for the open_files

I read that table_open_cache is tightly related to open_files, but how to tweak ?
thank you.