I am working with a very big (~10^5) number of files stored in a single folder. I am thinking about increasing this amount to 10^6.

1/ Could this be bad somehow for filesystem (ext3)? For example making it slower for overall use.
2/ What is the maximum amount of files eligible to be present in one folder?
3/ What is the best way to store a big number of files?
4/ What database would you suggest to use in my case?

Thank you for your time.