Is it possible, that one day, cpwebhosting servers will be short of disk space, as it is continously adding more and more reseller accounts.

I don’t think, this will happen, as when a particular type of server have adequate number of customers, it is closed and new server is added

Plan Disk space is allocated on these servers as a web space(server space for storing your web applications files/log files etc.), Database space(database type MS SQL (Windows) or PostgreSQL/MySQL/Oracle (Linux) disk space) and Mail space.

Web space server depends on the type of web hosting selected ie Windows Server or Linux Server.

MS SQL (Windows) or PostgreSQL/MySQL/Oracle (Linux) disk space) is created on respective server. MS Access database is created in Web server.

Mails are stored on Linux server running Qmail application.