PARTITION A USB HARD DRIVE
In this section I'm going to show you how to use the application called Disk Utility to split one usb hard drive into three disk partitions (logical drives) and how to
format (erase and restructure) those partitions (logical drives) so that they can work with an Apple Mac computer and/or a Windows computer. This examples in this section
can also be used to split a usb flash drive into partitions (logical drives).
In this particular lesson I will be splitting (partitioning) my 250GB USB Hard Drive into three partitions; one formatted (erased and restructured) for use with the Apple Mac operating system (OS X Mountain Lion) and the other two formatted (erased and restructured) for use with the Microsoft Windows 7 operating system. You can format a partition for use with OS X (Mountain Lion) only or for use with both Windows 7 and OS X (Mountain Lion).
One thing to note here is that Windows 7 will only be able to view the content of an hard drive that has been formatted (structured) as a Windows (MS-DOS File System)
partition (logical drive) whereas OS X (Mountain Lion) will be able to view the content of an hard drive that has been formatted as either a Windows (MS-DOS File System)
partition (logical drive) or an OS X (Mac OS Extended (Journaled)) partition (logical drive). More about the file systems and logical drives in a minute.
To split a USB Hard Drive (or USB Flash Memory Drive) into one or more partitions (logical drives) begin by inserting it into a spare USB Socket (Port) and then double click on the DISK UTILITY.app icon, located in the UTILITIES sub-folder of the APPLICATIONS folder, to launch (run/execute) the actual Disk Utility application (file).
When the Disk Utility application launches it will list your internal hard drive (i.e. Toshiba) and any external drives by default (normal behaviour). In this example (below) it is listing my internal 500.11GB Toshiba Hard Drive which has one partition (logical drive) called Macintosh HD and my external 250.06GB SeaGate USB Hard Drive which has one partition (logical drive) called UNTITLED. At this point you need to click on your listed USB Hard Drive (in my case on 250.06 GB SeaGate.....) and then on the PARTITION Tab (window).
Do not click on a listed partition (logical drive), such as UNTITLED, as this will not display the PARTITION Tab (window). You need to click on your listed, main, usb
hard drive (i.e. 250.06 GB SeaGate.....) in order to display and use the PARTITION Tab (window). This is because all partitions (logical drives) are mounted (created as
separate logical drives) on the main usb hard drive and therefore can only be removed (unmounted) from or added to (created on) the main usb hard drive using the
PARTITION Tab (window). In other words, adding or removing (mounting or dismounting) a partition (logical drive) can only be done when the main usb hard drive is
selected. If a listed partition is selected instead it is technically "in use" and therefore cannot be unmounted (removed) or be extended with other added (mounted)
partitions (logical drives).
Don't worry if the above explanation flew right over your head!! All you need to know and do here, as said above, is to click on your main, listed, usb hard drive and then click on the available PARTITION Tab (Fig 1.1 above).
As said above; the PARTITION Tab (window) allows you to create the one or more partitions (logical drives) that make up your usb hard drive's storage as a whole device.
As well as allowing you to create the size of a particular partition it also allows you to specify how that particular partition will be formatted (erased and structured
for the storage and indexing of folders and files).
In this example my usb hard drive is currently formatted (structured) to use the Windows (MS-DOS FAT) file system (the Windows method of storing and indexing folders and files). This means both Windows 7 and OS X (Mountain Lion) can view the content of this particular partition - They will both be able to view any folders and files I store on this particular partition. However, if I change the format (structure) of the partition so that it uses the Mac OS Extended (Journalled) file system only OS X (Mountain Lion) will be able to view the content. So this begs the question "Which file system should I use?".
The answer to this depends on what you are going to use your usb hard drive for. As a computer engineer you might need one partition formatted (structured) with the Windows (MS-DOS FAT) file system and another partition formatted with the Mac OS Extended (Journalled) file system. On the other hand; if you are purely an Apple Mac user and never need to store Microsoft Windows files on your usb hard drive then you would have one partition only formatted with the Mac OS Extended (Journalled) file system. Remember though, there are cross-platform files (files that work on both computers) such Microsoft Word (.docx) files, so even though you may be a total apple mac user at some point you might need to copy/read Microsoft Word 2010 files (created on Windows 7) from a usb hard drive that is formatted with the Windows (MS-DOS FAT) file system.
Now with a better understanding of partitions and file systems, I hope!, it's time to do the actual splitting up of the main usb hard drive into individual partitions
(logical drives). So at this point make sure you have selected (clicked on) your listed usb hard drive and then clicked on the PARTITION Tab (as explained/exampled above).
In this example I am going to create three partitions all in one go, as opposed to one-by-one, simply because I am sure I only want/need three partitions. This is done by selecting (clicking on) the 3 PARTITIONS menu-item from the PARTITION LAYOUT drop-down menu (below). If you're not sure how many partitions you require you could create two now for example and then add more later. It is possible.
After selecting the number of new partitions you, initially, require the PARTITION LAYOUT window pane will change from a representation of the current number of
partitions on your usb hard drive (one partition in this example) to a representation of the number of new partitions you have just selected for creation. Hence the
word CURRENT. Each new, respresented, partition will then be named after the current (main) partition of the usb hard drive. In this example UNTITLED 1, UNTITLED 2 and
As of now only one physical partition exists on my usb hard drive (UNTITLED). If I were to unplug my usb hard drive, restart my computer and then plug my usb hard drive back in Disk Utility would still state one physical partition available (UNTITLED) and not three. This is because the three new partitions have not been, physically, created yet. I first need to click on the APPLY button.
Before clicking on the APPLY button its worth noting, as in this example, that although the FORMAT setting currently states Mac OS Extended (Journalled) and is implying that any new partitions will be formatted with the Mac OS Extended (Journalled) file system (Fig 1.3 below), they will in fact be formatted with the Windows (MS-DOS FAT) file system. Why? Because the usb hard drive as a whole is currently formatted with the Windows (MS-DOS FAT) file system. Splitting its one partition into three partitions for example means those three new partitions will still inherit (be formatted in) the current format - Windows (MS-DOS FAT) file system. As well as repartitioning your usb hard drive you might also want to rename, resize and/or reformat each new partition before clicking on the APPLY button - Ammendments will only be physically actioned (partitions will only be physically created) when you click on the APPLY button.
To rename, reformat and/or resize a particular partition you must first select it by clicking inside its rectangle/square preview pane (PARTITION LAYOUT window pane). From there you can click inside its NAME edit box to rename it. In this example I have already changed the name UNTITLED 1 to WINFILES because I will be using the first partition to store my WIN-dows FILES. I have kept the FORMAT drop-down menu selected on MS-DOS (FAT) to denote I would like this first partition to be formatted with the Windows (MS-DOS FAT) file system. And I am now changing the partition size to 50GB.
In this next example I am currently selecting Mac OS Extended (Journalled) from the FORMAT drop-down menu as I want the second partition, which I have already renamed to OSXFILES, to be formatted with the Mac OS Extended (Journalled) file system. I will change its size to 50GB afterwards.
For the third and final partition I will rename it STORAGE and keep its FORMAT drop-down menu selected on MS-DOS (FAT) so that it will be formatted with the Windows (MS-DOS FAT) file system. Its size will be dictated by the other two partitions, meaning it will use the remaining size (capacity / available storage space) of the usb hard drive. So the first and second partitions will each use up 50GB of storage space leaving the remaining 150.06GB of available storage space for the third partition. All that's left to do now is click on the APPLY button.
Clicking on the APPLY button brings up the following Warning message requester that asks you if you really want to delete the current partition(s) and its/their data in order to create your new partition(s). If you are absolutely sure you don't mind losing any data on the current partition(s) click on the PARTITION button to continue. Obviously you would, and should, of made a backup copy of your usb hard drive before repartitioning it. If not, for whatever reason(s), make a backup copy before clicking on the PARTITION button.
As you can see from the above; The three new partitions have been created successfully. The WINFILES and STORAGE partitions have both been formatted with the Windows (MS-DOS FAT) file system and the OSXFILES partition has been formatted with the Mac OS Extended (Journalled) file system. Here is what their desktop icons look like.
Because the three partitions have been mounted (created as three separate, Logical, Hard Drives) they can be treated as such. For example. When you go to eject (dismount) any one of the mounted partitions (separate logical drives) you will have the choice of dismounted the one you selected or all of them. So in this example I could eject (dismount) each partition (logical drive) in turn (i.e. WINFILES first, STORAGE second and OSXFILES last) or EJECT ALL in one go.
I have said Partitions above, just so that you can understand this lesson more, but you should get into the habit of calling them Logical Hard Drives; which in this
case is just a fancy wording for Mounted Partitions. Basically three separate hard drives have been created using one hard drive! These separate hard drives are now
known as Logical Hard Drives. They are also known as Partitions simply because they were created (split/partitioned) from one main hard drive.
Whenever you make partition changes to a usb hard drive a Time Machine window will appear to ask you if you would like to use that usb hard drive or one of its partitions as a storage device for the Time Machine feature of OS X (Mountain Lion). You will only be able to use partitions that have been formatted with the Mac OS Extended (Journalled) file system as these next two examples show.
If you don't want to use the Time Machine feature simply click on its DON'T USE button, otherwise click on its USE AS BACKUP DISK button.
Hopefully this section has made the process of creating and understanding Disk Utility, and Partitions in general, a little easier. In the next section I will be showing you how to use the usb hard drive with the Time Machine feature.