A. NAS's obvious advantage over SAN is ease of administration, but either option will provide similar overall performance. (For an in-depth comparison of these two storage solutions, see Barrie Sosinsky and C. Thi Nguyen, "NAS vs. SAN," Windows 2000 Magazine, June 2000.) For your capacity requirements, I suggest that you consider a Network Appliance (NetApp) NAS solution or a Dell, EMC, or Hitachi SAN solution. The providers' prices vary, but you can expect to spend between $30,000 and $70,000.
NetApp's NAS devices support both Oracle and Exchange Server. I know of several companies that run Exchange Server on NetApp boxes, and the companies seem to be happy with the performance. I recommend the F700 series, which starts with the NetApp F720. This product, which has a maximum capacity of 500GB, should meet your needs; if you eventually need to expand beyond your current requirements, you can upgrade to the NetApp F740 or NetApp F760. NetApp has recently released a new product, the NetApp F85, which is geared toward smaller companies and branch offices. Although the solution is SCSI-based rather than fibre channelbased, performance is better than on the NetApp F720. The NetApp F85 can scale to 648GB; pricing for the base model starts at less than $20,000. (For more information, see the FAQ about NetApp F85.)
As far as SAN solutions go, Dell's PowerVault 650F and PowerVault 660F scale to about 8TB. (Dell is positioning the PowerVault 660F, which costs less, has a smaller form factor, and supports upgrades to 2GB fibre channel, to replace the PowerVault650F.) The EMC CLARiiON FC5300 scales to 2TB. Hitachi's Hitachi Freedom Storage 5800 scales to 1TB. Any of these solutions will meet the needs you describe.