It is running gigabyte switches. It is not running Exchange. I never thought of having two separate raids. I’m assuming you would need two raid controller cards then? It does not seem slow to “file serve”, but the SQL application just seems sluggish. I figured increasing the ram (sbs2003 could only go to 4GB) would help, but I wondered if teaming a pair of nics would also help (I don’t want to speed up one process to find the slowness has moved to another aspect.
You generally can have different RAID volumes on a single array [of disks]. You can also seperate disks into different arrays and assign them different drive letters (or mount points). This is the best to do for DBs, one volume for DBs, one for logs. Depending on the database usage (heavy writes) this can be useful. But for small implementations it is generally not necessary.
If you have two NICs, one thing you can do without bonding is separate your traffic. SQL (port 1433) can be assigned to use a particular IP. You could assign one NIC (and IP) for SQL and the other NIC (and IP) for "everything else".
In order to discover what is really going on (and what you need), I would recommend using perfmon (Performance Monitor) to capture some statistics on CPU, memory, disk, and network usage. This way you can see what the bottlenecks are, and design around them.
I would think, though, the replacing this server (which is probably 6+ years old) with something newer would have a profound impact on performance, even in a relatively default configuration.
For a configuration recommendation, it really depends on the hardware and budget.
I would recommend RAID-1 for the OS
I would recommend RAID-5 or 6 for the file server portion
Depending on the SQL DB size I would recommend RAID-5 or 6 if it is a "large" DB (doesn't fit on single disk in your planned array)
If the SQL DB size is "small" I would recommend RAID-1 with SSDs
If the SQL DB is heavily transacted, SSDs are definitely the way to go (if affordable). If you cannot use SSDs because it is a "large" DB, I recommend doing one volume for the DB (RAID 5 or 6) and one volume for transaction logs (SSDs in RAID-1 or larger drives in RAID 1+0).
I would recommend RAID-5 for workstation backup, if you are going to use it. If there are not using this now, though, I tend to recommend against it. This type of store can grow quickly and it's better to have users store important things on a file server that is backed up instead of relying on you to backup their workstations.