On a Windows machine, the Steam application allows you to relocate the “SteamApps” folder to a different drive. This allows you to effectively shift your content around anywhere you like. When you install a new game, it’ll even ask you where you want to install it.
For some bizarre reason they did not afford the same convenience to Mac users. Initially when Steam was released for the Mac they even forced you to keep the SteamApps folder in your Documents folder. This made it really painful to use a portable home directory. Valve relented after a huge user outcry and relocated the folder to ~/Library/Application Support/Steam, which is probably where it belonged anyway.
Now what if you want to move it out of there to an external drive? I have roughly 40gb of games wrapped up in that directory and frankly, there’s no reason for it to exist in my home directory. I studied around on the forums and Steam support site and discovered they did not have any ability to shift this content around natively. That won’t defeat me, however.
I moved the SteamApps folder to a location on an external drive and first tried to make an alias of the new location to ~/Library/Application Support/Steam/SteamApps. This didn’t work. When I launched Steam, it told me that it had to exist on a case-insensitive volume. That’s rather odd. My external drive is formatted with HFS+ case-insensitive. No matter. I deleted the alias and tried a UNIX-style link:
ln -sf /Volumes/DS4600/Storage/SteamApps ~/Library/Application Support/Steam/SteamApps
I then started Steam back up and I heard the DS4600 RAID-5 volume (which is where the SteamApps now reside) spin. I looked in the library and voila, all of my games were present.
That wasn’t so hard. Wonder why Valve won’t let you do this? I’ll keep it running this way for a while and see if it blows up.