Apple has its own reasons for doing what they do; they're certainly entitled to do so. You see, Apple is very focused on getting brand-new Mac customers and, in particular, those coming to the Mac with iOS experience, to not have to think about a "file system" where folders and files can be moved, copied, renamed, deleted, and otherwise manipulated.
Accordingly, Apple's tendency of late has been to turn off some features that, let us say, the more "seasoned" Mac users are accustomed to. One of these is the subject of this article.
By default on new machines or freshly installed OS X software, there are some disabled settings that prevent you from seeing volumes mounted on the desktop. To someone used to seeing the familiar icons, this is most disconcerting. Here's how to bring them back; the solution being found in Finder Preferences.
Don't confuse this with System Preferences. You need to go to Finder Preferences by first making sure you are in Finder. You know you're there if the Finder menu appears in the menubar right next to the Apple menu. If not, click anywhere on the desktop to make Finder active. Go ahead and open the Finder menu. Select Preferences, and click on the General tab if not already selected.
You'll notice that the section under "Show these items on the desktop:" lists a number of storage devices (hard disks, external disks, CDs, etc.) that can be mounted and visible on your desktop. Enable the devices you wish to be able to view on your desktop by clicking the appropriate checkboxes. These changes will be permanent until you should decide to disable them. Also, don't forget that all settings in Finder Preferences pertain only to the user account you are currently working in.
Select which devices you want to see mounted on your desktop.
While in Finder Preferences you can also set these storage devices to appear on the sidebar of any open Finder windows. Click on the Sidebar tab in Finder Preferences. You will see all the items that can appear in the Finder window sidebar, including the storage devices we are interested in. They will be listed in the "Devices" section of your Finder window sidebar.
In the Sidebar pane you can control what's viewable or hidden in the Finder window's sidebar.
The listing you see in the Sidebar section of Finder Preferences reflects what you see in the sidebar of any Finder window you open. You will also see this in File-Open and File-Save panels. Notice, too, that you can have your Mac appear listed under "Devices" in the Finder sidebar. That's right, your Mac is considered a "Device."
A Finder window showing my Mac listed in the sidebar, letting me access all storage "volumes" available to me.
This gives you direct access to the root (top) level of your your internal drive, any additional attached drives, USB flash drives, iPods, optical discs as well as access to any networked storage devices and servers.
Finally, you can re-arrange the order of the items in the "Favorites" (called "Places" on older systems) and "Devices" sections of the sidebar, but you don't do this in Finder Preferences. You need to do this while you have a Finder window open. Simply drag the items up and down to your liking within those sections of the sidebar. Any changes you make to how everything is listed, what's hidden, and what's showing will be reflected in any other Finder window you open from that point on.
Did you know that you can customize the Finder window sidebar to include your own folders and files? Yes, you can manually add any folder or file you want into the "Favorites" section at the top of the Finder window sidebar. In older versions of OS X, this section is called "Places." This makes your custom folders and files readily available to you. Adding a folder is straightforward. Simply drag it to the sidebar, placing it where desired.
I can drag any folder or file to the sidebar of a Finder window.
Placing a file in the sidebar is done a bit differently in Lion and Mountain Lion; you need to hold down the Command key while dragging and placing. The action of adding files and folders to the sidebar actually creates what amounts to an Alias of your item, but the real one remains in its original location. When you drag an item to the sidebar be careful that you don't accidentally drop it into another folder already listed there.
To remove the folder or file from the sidebar - remember, you are not removing the original - simply drag the item straight out of the sidebar as if moving it to the desktop. As before, if you are using Lion or Mountain Lion, you need to do this while holding down the Command key. When you let go, you should see a confirming "puff of smoke" and hear a satisfying "poof" sound as your folder disappears.
Oh, I almost forgot. You can right-click (or Control-click) on any sidebar item to view other actions you can take on the item. For example, this is the only way you can rename your custom items you've placed in the "Favorites" section of the sidebar.
In the final illustration below you see what the "Favorites" section of Finder windows sidebar looks like on my machine; how it's configured, which items I enabled, and how I ordered them. Of course, yours many look differently, but you might get some ideas for your own organization.
This is how my Finder window sidebar is currently organized.
We have explored how to enable the viewing of attached storage devices on our desktop. Over the years, I have observed that many Mac users are not aware of Finder Preferences. I'll tell you what I tell them: by exploring your options, you can find many other ways to personalize how things look and behave on your Mac. After all, it is a personal computer, right?