It is small office with 15 users and domain controller with limited storage space on it available. All users initially put their files on shared folder but over time amount of data grew a lot so we were forced to store files on couple external drives connected locally to workstations. We're looking for solution which will allow us to use shared folders to store all the data currently spread between several places, assign access permissions and extend it in the future if necessary. This solution should provide some redundancy and fast access to files so multiple users can access these files at the same time. I tested Thecus NAS enclosure with 2x750GB drives in RAID1 but it is too slow and limited as functionality. I was also thinking about adding 2 more drives inside the server (2x1.5TB in RAID1) but I am not sure that I have enough SATA ports inside and actually not sure that built-in Intel Matrix RAID currently used for storage array can operate multiple RAID sets. The server is tower so we're not looking at rack-mountable solution until it is the only option available. I am net familiar with file servers, but would be separate server with Windows 2003 Standard, hardware RAID with enough ports a good solution, what do you think? How actually businesses expand their storage? I'm looking forward for your opinions and thoughts.
P.S. The price is also a factor as right now we cant's spend $6000 or more just for storage, especially during recession. We'll be adding about 1GB data daily to shared storage. We are not looking for expensive solution. New storage will be used for backups as well (for example, we can backup Exchange database from Domain controller to it).