I am using a Mac Mini as a file server with OS X Snow Leopard - Standard, not Server version so the GUI options could be different if you have the server edition. It took a bit of messing around to get things just the way I wanted them. Below is how I have things configured.
First turn on file sharing.
System Preferences --> Sharing
Tick the box for “File Sharing” and under “Options” select “Share Files and Folders using SMB (Windows)”.
Next if you just want guest access to the network shares (i.e. no username/password) then go to
System Preferences --> Accounts
Select the Guest account and tick the box to allow guest accounts to connect to shared folders. If you don’t want to use a guest account then you need to create a OS X login account then use the username/password when you connect to the network shares.
Now you need to make sure your all your computers are in the same Windows workgroup
System Preferences --> Network
Select your Network Adapter and click advanced. Go to the WINS tab and fill in the Workgroup field the same for each PC on your network. I don’t think your OS X clients are too fussed but Windows needs to be identical.
The final step is now to share out the Drobo. You can share out the whole disk (/Volumes/Drobo) or subfolders as necessary.
If you select the Drobo in the finder and right-click on it and go to “Get Info” you can enable the sharing options. I really could not get this to behave the way I wanted - permissions only seem to apply to the top-level folder and not subfolders.
If you want to do it manually then you can edit the file /etc/smb.conf in a text editor. Just add your sections to the bottom of the file. A read-only and read-write example is below
path = /Volumes/Drobo/myfolder1
writeable = yes
public = yes
path = /Volumes/Drobo/myfolder2
writeable = no
public = yes