Flexible storage management solution

["Truong Duc Luong" <luongductruong () gmail com>]

Hi,

I looking for a storage management solution. It can:
- User management: 5000 - 10000 users.
- Flexible quota management: 
        + set maximum quota for each user
        + Sharing free user's quota to another user: it's for optimal the
storage system
- Security

In some point, this system operate like Rapidshare.com. Any suggested
solutions? Pls, share for me and others.

Thanks
Luong