Ordinary Mac users would not much care about what sort of file system Mac uses inside of internal/external storage device.  However, it becomes very important when you decide to upgrade Mac computer operating system (macOS) to the latest High Sierra.

If you require Mac computer internal storage upgrade service (Sydney CBD, Sydney North Shore – particularly in Chatswood, Roseville, Lindfield, Killara, Gordon, Pymble, Turramurra, Wahroonga, Warrawee, Hornsby, Macquarie Park and St Ives area) please contact Harry 0417 424 909.  Or refer to our Service page.

Part I: Basics

HFS Plus or HFS+ is a file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the release of the Apple File System (APFS) with macOS High Sierra in 2017. HFS+ is also one of the formats used by the iPod digital music player. It is also referred to as Mac OS Extended or HFS Extended, where its predecessor, HFS, is also referred to as Mac OS Standard or HFS Standard. During development, Apple referred to this file system with the codename Sequoia.

Enough for computer jargons.  In a nut shell, HFS or HFS+ has been around about 30 years.

Pros of Apple’s HFS+

  • Supported on all versions of Mac OS X and macOS
  • Encrypted volumes are accessible by any version of Mac OS X and macOS
  • Supports Fusion drives (Also called as “Hybrid Drive” – combination of conventional hard drive and SSD)

Cons of Apple’s HFS+

  • Concurrent access of the file system by a process is not allowed.
  • No snapshots
  • No support for dates beyond February 6, 2040 (My MacBook Pro would not last that long anyway)
  • Limited native file support for other file systems
  • Timestamps do not use the nanosecond standard.
  • Checksums for data integrity is missing.

about APFS

So, what about new APFS (Apple File System)?

Pros of Apple’s APFS

  • Allows for clones or multiple copies of the same file, with only changes stored as deltas, which reduces storage space when making revisions or copying files
  • Can create point-in-time snapshots
  • Full-disk encryption with single or multi-key encryption for added security
  • Uses checksums for data integrity of metadata
  • Metadata corruption prevention due to creating new records instead of overwriting existing ones, which can become corrupt due to system crashes
  • Increases performance on some devices by eliminating the need to write changes twice compared to HFS+ Journaled file systems
  • More efficient management of storage typically yields additional free space.

Cons of Apple’s APFS

  • Checksums are only for metadata integrity—not user data
  • Very important issue:  Cannot be used for a Time Machine backup drive (Backup drive must be HFS+ otherwise it will not work)
  • Compression is not available.
  • Encrypted volumes can only be accessible by other computers running macOS High Sierra
  • Does not support Fusion drives (Looks like we have to wait until the next macOS release 10.14 of *Mojave)
  • Cannot utilize *NVRAM for data storage

*Mojave: Next macOS due to be released in this coming September or October, 2018.  Named after the Mojave Desert is an arid rain-shadow desert and the driest desert in North America.  Due to the feature “Metal”, a graphics framework Apple originally introduced for iPhones, iPads and iPods, Mojave runs only on following Mac computers.

iMac models from 2012 or later
iMac Pro 2017 or later
MacBook  from 2015 or later
MacBook Pro from 2012 or later
MacBook Air from 2012 or later
Mac mini from 2012 or later
Mac Pro from late 2013 (plus mid 2010 and mid 2012 models with recommend Metal-capable GPU)

Where as High Sierra runs on;

iMac: late 2009 or newer
MacBook/MacBook (Retina): late 2009 or later
MacBook Pro: mid-2010 or later
MacBook Air: late 2010 or later
Mac Mini: mid-2010 or later
Mac Pro: mid-2010 or later
iMac Pro: 2017 or later

So, almost all the Mac computer released between 2009 and 2011 will not run this new coming macOS.  Sorry guys, but that the fact of life.

*NVRAM (Non-volatile random-access memory) is random-access memory that retains its information when power is turned off. This is in contrast to dynamic random-access memory (DRAM) and static random-access memory (SRAM), which both maintain data only for as long as power is applied.

Again, enough for computer jargons.  But it’s very important which file system you choose when you upgrade your Mac computer to High Sierra.

Part II: Upgrade your Mac operating system to High Sierra

Recently, I dealt with internal PCIe SSD storage upgrade for my client’s 2014 MacBook Air.  When it comes to hardware upgrade, Mac computers are not user friendly at all.  Outside service providers are almost off limits.

Recent Mac computers use very specific Apple factory issue parts.  Almost each year of make uses different internal storage parts. (I simply do not understand why, though.)  And they are very expensive.  Standard MacBook Air comes with very limited 128GB internal storage space.  If you have very large iCould photo library syncing with your MacBook Air, 128GB storage will soon run out.  To find alternative affordable internal storage device was not easy at all.

According to my research, I nailed down 2 candidates for the upgrade.

1. Super Blade
Super Blade SSD

512GB: US$579.00

Very expensive.  But it is said Mac computer will see this storage device as OEM made one and does not have any compatibility issue.

2. OWC Aura Pro X

OWC Aura Pro X SSD

SSD Upgrade Kit Includes: SSD, tools & transfer enclosure
OWC Aura Pro X SSD upgrade kit
240GB US$169.75
480GB US$229.75
1.0TB US$329.75
2.0TB US$549.75

Note: Aura Pro X is designed for APFS file system available on macOS 10.13 High Sierra or higher. Upgrade to macOS 10.13 or higher before Aura Pro X SSD install.

Enclosure can only work with the original Apple factory issue SSD

Because of budget reason and it comes with an enclosure case can be used for the original SSD as extra storage space, we decided to get OWC Aura Pro X SSD upgrade kit 240GB.

Then, the fun started.  My client’s MacBook Air 2014 was already updated to High Sierra.  However, when I installed the OWC Aura Pro X SSD, MacBook Air would not recognize it at all.  It took me a while to figure out why.  For MacBook Air to recognize this SSD, the original SSD must have been updated to the latest High Sierra (currently ver 10.13.5).  So, obviously  OWC Aura Pro X SSD has a compatibility issue.

Following article clearly indicates it.

OWC’s Aura SSDs Not Working With macOS High Sierra, Fix Coming Soon

Unlike Windows base PC computer where basic “Firmware” (specific class of computer software that provides the low-level control for the device’s specific hardware) stored in the build in computer chip, macOS holds this information in a file system residing in a recovery partition of the system.  In other words, it’s software based not hardware based information.


Mac computer does have an equivalent of BIOS (Basic Input Output System) in PC architecture chip called SMC (System Management Controller).  But functions of SMC is far limited comparing with the BIOS in PC computer.

The SMC is responsible for these and other low-level functions on Intel-based Mac computers:

  • Responding to presses of the power button
  • Responding to the display lid opening and closing on Mac notebooks
  • Battery management
  • Thermal management
  • Sudden Motion Sensor (SMS)
  • Ambient light sensing
  • Keyboard backlighting
  • Status indicator light (SIL) management
  • Battery status indicator lights
  • Selecting an external (instead of internal) video source for some iMac displays

OK, it’s finally recognized by MacBook Air.  Next step.

If you prepare the OWC Aura Pro X SSD as HFS+ file system drive using Disk Utility of Mac, then High Sierra will be installed on HFS+ file system.  Whereas if you erase a partition of OWC Aura Pro X SSD setting as APFS file system and install High Sierra, High Sierra will be installed on APFS file system.  Also, if your try to restore Time Machine backed up file to this new SSD, it will not work.  So, it requires the original SSD to be placed in a enclosure and manually copied back the new drive (Gave me much extra work, sigh!).

Once file system becomes APFS, there is no easy way going back to the old HFS+ system, though. (It’s possible, but it’s a hassel)

Updated on 9/1/19

Those who are interested in converting APFS to HFS+ without losing the data, please refer to my following post.

Apple Myth 06 – macOS Mojave and APFS

Unlike High Sierra, Mojave will not give you any choice of file system but APFS.  So High Sierra with HFS+ users, please be aware this when you update your operating system.

Update end;

Another matter is that APFS system drive will not startup if you use as external  connected USB drive. (I tested with my MacBook  Pro).

So, It’s all up to you which file system you use with High Sierra for your favorite Mac.  But think twice before you decide to do so.

For your further information, please take a look at the following stats for desktop macOS Version Market Share (Worldwide and Australia 06/17–05/18)

Updated on 22/6/20

If you choose APFS system drive as start up drive for those Mac devices can run APFS system, there is no problem starting the system even the system disk is connected through external USB enclosure (tested on my iMac 27 inch late 2013).  The reason for APFS external USB connected drive did not start up for my 1/9/19 update (just above) is to do with the firmware on my MacBook Pro at that time was for El Capitan (10.11) and there was no way to recognise APFS file system.   Also, please refer to my recent blog post for more affordable PCIe SSD (NVM2) upgrade. 

======= Update end ========

Courtesy of statcounter

a. Worldwide

macOS Users Stats Worldwide

StatCounter macOS WW

b. Australia

macOS Users Stats Australia

StatCounter macOS Australia

It appears High Sierra achieved very steep spike in the share in last 6 months.  Unlike Windows 10, Mac users are not forced to upgrade macOS operating system.  Many of my friends are still using OSX 10.10 (Yosemite).

Update: 04/07/18

Just about a week ago, I got a nice MacBook Pro Late 2013 with Ratina Display which was no longer in use.  The MacBook Pro has a basic configuration (4GB on board ram – not up-gradable, 128GB PCIe Apple factory issue SSD).  As internal storage of 128GB is too small for me, I’m planning to replace the 128GB SSD with bigger capacity one.


  1. Apple would never sell you any parts of Mac computers.  First time I heard this from an Apple shop assistant, I just could not believe what I was hearing.  But it’s true.  Once you buy your Mac Computer, you have to live with it as Apple will only replace the original spec parts if it becomes faulty.  And you have no choice but go through their service program.
  2. You can purchase Mac Computer parts online to replace it or upgrade it yourself.  But bear in mind, the action voids Apple warranty (if it’s still under warranty).
  3. As much as I highly respect dedicated Apple National Support Program, you have to know one thing for sure.  Apple will provide you the best possible support so long as you follow and agree to their terms and conditions.

So, whatever I choose to do with this MacBook Pro, it will be on my own risk.  No big deal.  What I’m looking at this moment is a message board thread of MacRumors.

Upgrading 2013/2014 Macbook Pro SSD to M.2 NVMe

There are 1600 posts already on the board.  It means I will purchase an adapter and M.2.NVMe SSD replacing the original Apple factory issue SSD.  Tons of information is already there and you have to decide yourself.  It will be a very interesting project for me.

If you need help for upgrading internal Apple internal storage (Sydney CBD, Sydney North Shore – particularly in Chatswood, Roseville, Lindfield, Killara, Gordon, Pymble, Turramurra, Wahroonga, Warrawee, Hornsby, Macquarie Park and St Ives area) please contact Harry 0417 424 909.  Or refer to our Service page.

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