Perhaps the most important element that we take for granted when it comes to our Mac computers (and any computer in general) is their storage.
As the storage in our computers has expanded, it has also become
increasingly complex. And learning about at least part of that
complexity can provide you with a better understanding of what goes on
‘behind the scenes’ whenever you use your Mac.
In this article, we take a look at the storage technology used by
modern Mac computers: What it is, how it works and how its integration
provides Mac users with a (relatively) painless and smooth experience
when using their computers.
Partition Schemes
One of the most important elements of any disk is its partition scheme.
A partition defines the limits or boundaries of a storage disk.
Applying a partition scheme to a disk is the process of applying certain
logic parameters to it. Even if you have multiple partitions on one
disk, it is always necessary for each of them to have its own partition
scheme.
The latest versions of OS X support three types of partition schemes:
GUID Partition Table (GPT): This is the partition
scheme used as default by Mac computers. It is used by all Intel Macs
(and by older models running OS X v10.4.6 or later) and is also
supported by Windows Vista or later.
Apple Partition Map (APM): The default partition
scheme used by older PowerPC Macs, mainly to start up from. Newer Mac
models also support this type of partition scheme, but no version of
Windows includes native support for it.
Master Boor Record (MBR): The default partition
scheme used by non-Mac computers, hence it is also the one you are most
likely to find applied on most new drives and devices that use some sort
of internal memory. Even so, this partition scheme is also supported by
Macs.
Once you have your disk partitioned, it is time to apply a format to its volume/s.
Volume Formats
The format applied to each of the volumes on a disk define how your
files will be saved to it. This is especially important when it comes to
compatibility since you might want your files and disks to be easily
accessible by some computers (friends and family for example), so it is
always wise to consider which volume formats they use.
Here are the volume formats supported by OS X as read/write:
Mac OS Standard: The older volume format used by previous versions of Mac OS. Considered legacy and rarely used anymore.
Mac OS Extended: Another legacy volume format. It is actually an upgraded version of the Mac OS Standard format.
Mac OS Extended (Case-Sensitive): A volume format
created to address the issue of volumes that do not differentiate
between file names written in lower and upper cases. However, this type
of Volume format displays a series of issues with some third party
applications, which is why it is not supported by default by OS X client
systems.
Mac OS Extended (Journaled): An additional option
for the ‘Extended’ volume format that adds advanced file-system
journaling. With it, the system monitors all the operations that files
go through at any given moment, which in turn helps prevent file
corruption and also makes the check and repair process after a crash a
lot smoother.
Mac OS Extended (Journaled, Encrypted): This format type adds full disk, XTS-AES 128 encryption.
File Allocation Table (FAT): The FAT format is one
of the most popular ones out there. And with every iteration, it
supports larger volumes (that’s where the FAT12, FAT16 and FAT32 names
come from). The format is also used by Mac OS X’s Apple Boot Camp to run
Windows XP (from a FAT32 volume), but OS X itself cannot start up from
this volume format.
Extended File Allocation Table (ExFAT): This format was created specifically for large flash storage disks of the type coming out more often lately.
UNIX File System (UFS): As its name implies, the purpose of this volume format is to support UNIX systems.
As for the volume formats supported by OS X as read-only, they are:
New Technology File System (NTFS)
ISO 9660 / Compact Disc File System (CDFS)
Universal Disk Format (UDF)
Core Storage
Core Storage is one of the most important elements of OS X file
management system. What it does is add a management layer between a
partition scheme and the volume formats of a disk.
This, of course, adds complexity to the file system, but at the same
time, it provides it with great flexibility, allowing it, for example,
to encrypt and decrypt a volume without interrupting its normal
operation (a function that is essential to FileVault). Phil Schiller explaining Fusion Drive at an Apple Event
Core Storage is also an essential component of the now popular Fusion
Drive technology available in some Macs, which run various disks as if
they were one. This technology is also a reliable and safe way to store
data.
Conclusion
As you have seen in this article, the way your Mac’s storage works
goes much deeper than it might seem at first. Understanding how it all
works might not be mandatory for every Mac owner, but knowing how it all
comes together will definitely help you make better decisions when it
comes to managing your Mac’s storage.