Precision Workstation 390 and maximum hard drive size

Other than some threads about older laptops I don't think I've ever seen any SATA controller that had a harddrive size limit, so 1.5TB drives should be fine.

One note though: you cannot boot to a (virtual) disk that's over 2TB in size. This is a limitation of having a bios in a computer. You may be able to use the matrix raid to carve the 4-disk raid 5 into 2 pieces where the first piece is below 2TB and the 2nd piece can be whatever size you want.

Another note: To use a disk over 2TB (as a data disk), it needs to be converted to GPT (GUID Partition Table (see wikipedia for more detail)). If you're using Microsoft Windows, this requires XP x64 or Vista. Windows XP 32-bit cannot use disks over 2TB. If you're wanting to run a Microsoft server OS, you have to run 2003 SP1 or later. When using Linux (not sure if this will be compatible with Intel's matrix raid though), as far as I know you have to run kernel 2.6 or later to be able to use a GPT disk.

That's some very helpful info, thank you!  This machine is simply going to be used to store large files for a small office, so I think I'll go the XP X64 route.  So what you're saying is that I should (in the SATA bios) create a small container  in the RAID 5 (40 gig or so should be PLENTY) for the boot drive and leave the remaining space for the data container, or did you mean something else?

Yes. Something to that effect. XP x64 is a fairly small footprint (compared to Vista), so 40GB gives enough room for the OS, swapfiles, service pack upgrades (some of these can use 1GB+ during the install process).

Then when in the OS, if you haven't created the 2nd raid 5 yet, you create this using the Intel Matrix raid manager. If you already had it created the next step is to go to disk management. You will see the 2+TB disk as if it's split in 2; the first part is 2048GB (2TB) and the 2nd part is the rest. This 2nd part is completely unusable (right clicking doesn't allow creating a partition or do anything). Right click the disk (not the partition area); probably "disk 1", and select the option to convert to GPT. This will make the whole disk usable and you can partition it and format it. If the partition is over 4TB and you get some message about NTFS not wanting to format due to a sector size, in the partition/format wizard change the cluster size from 'default' (4kb) to 8kb or larger. Larger block sizes do waste more space if you have a lot of (small) files, but NTFS has a limit to the number of sectors the filesystem can keep track off, so if you exceed this number you may be forced to either use 2 partitions or go with a larger sector/cluster size.