Would creating folders for each user be stressful or slow the server down?

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http://stackoverflow.com – I'm creating a site where users can upload and share their files. I'm thinking about creating a folder for each individual user to upload their files. Would this slow the site down or cause trouble in the server? I'm not expecting a million users, but around 100,00 - 200,000. Seems like a lot of folders for each user. I also have another solution of just renaming the file when they upload, but I would like to keep the file name in tact so users still know which file is which. Edit: if it helps I plan on using Linux server. (HowTos)