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I recently bought an 14 inch MacBook Pro, which has 512GB SSD storage. When I check the capacity of the SSD in MacOS, it is reported as 494,38 GB in system report (494.384.795.648 bytes), which is about 5,6 GB less than what it should be (500 GB).

My previous MacBook Pro from year 2015, has an intel processor and 256 GB of SSD storage, and its capacity is reported as 250,79 GB (250.790.436.864 bytes).

Thinking that this 5,6 GB could be a difference specific to M1 Macs, I searched the internet and also found out that 256 GB SSDs of M1 devices are reported as 245,11 GB, which supports my hypothesis.

So, what is Apple using this 5,6 GB of SSD storage in M1 Macs? Did they start to do something like SSD provisioning? Caching to speed up things and etc with M1 Macs?

-- Later edit: As requested, I have added output of more detailed commands below. It looks like M1 Pro machine has an additional 5.4 GB recovery partition. which explains the difference. But now I wonder, why does my Intel machine does not have a recovery partition? The Intel machine had Os Mojave on it when I got it, I upgraded the OS to first Catalina, then Big Sur from inside MacOS as usual. I don't think I have deleted any existing recovery partition.

Output of command: "system_profiler SPNVMeDataType" on 512 GB M1 Pro machine:

NVMExpress:

Apple SSD Controller:

    APPLE SSD AP0512R:

      Capacity: 500,28 GB (500.277.792.768 bytes)
      TRIM Support: Yes
      Model: APPLE SSD AP0512R
      Revision: 386.40.1
      Serial Number: 0ba0160a2214342e
      Detachable Drive: No
      BSD Name: disk0
      Partition Map Type: GPT (GUID Partition Table)
      Removable Media: No
      S.M.A.R.T. status: Verified
      Volumes:
        disk0s1:
          Capacity: 524,3 MB (524.288.000 bytes)
          BSD Name: disk0s1
          Content: Apple_APFS_ISC
        disk0s2:
          Capacity: 494,38 GB (494.384.795.648 bytes)
          BSD Name: disk0s2
          Content: Apple_APFS
        disk0s3:
          Capacity: 5,37 GB (5.368.664.064 bytes)
          BSD Name: disk0s3
          Content: Apple_APFS_Recovery

output of command: "system_profiler SPNVMeDataType" on 256 GB Intel 2015 MacBook Pro:

  • this command does not give any output on this machine but instead, I can see the following information in the SATA section: of full system_profiler command output:

    Apple SSD Controller:

    Vendor: Apple
    Product: SSD Controller
    Physical Interconnect: PCI
    Link Width: x4
    Link Speed: 5.0 GT/s
    Description: AHCI Version 1.30 Supported
    
      APPLE SSD SM0256G:
    
        Capacity: 251 GB (251.000.193.024 bytes)
        Model: APPLE SSD SM0256G                       
        Revision: BXW1PA0Q
        Serial Number: S29CNYCG464909      
        Native Command Queuing: Yes
        Queue Depth: 32
        Removable Media: No
        Detachable Drive: No
        BSD Name: disk0
        Medium Type: Solid State
        TRIM Support: Yes
        Partition Map Type: GPT (GUID Partition Table)
        S.M.A.R.T. status: Verified
        Volumes:
          EFI:
            Capacity: 209,7 MB (209.715.200 bytes)
            File System: MS-DOS FAT32
            BSD Name: disk0s1
            Content: EFI
            Volume UUID: 0E239BC6-F960-3107-89CF-1C97F78BB46B
          disk0s2:
            Capacity: 250,79 GB (250.790.436.864 bytes)
            BSD Name: disk0s2
            Content: Apple_APFS
    

Output of command: "diskutil list" on 512 GB M1 Pro machine:

/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         500.3 GB   disk0
   1:             Apple_APFS_ISC ⁨⁩                        524.3 MB   disk0s1
   2:                 Apple_APFS ⁨Container disk3⁩         494.4 GB   disk0s2
   3:        Apple_APFS_Recovery ⁨⁩                        5.4 GB     disk0s3

/dev/disk3 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +494.4 GB   disk3
                                 Physical Store disk0s2
   1:                APFS Volume ⁨Macintosh HD⁩            15.7 GB    disk3s1
   2:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.7 GB    disk3s1s1
   3:                APFS Volume ⁨Preboot⁩                 316.2 MB   disk3s2
   4:                APFS Volume ⁨Recovery⁩                851.2 MB   disk3s3
   5:                APFS Volume ⁨Data⁩                    114.9 GB   disk3s5
   6:                APFS Volume ⁨VM⁩                      1.1 GB     disk3s6

Output of command: "diskutil list" on 256 GB Intel 2015 MacBook Pro:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI ⁨EFI⁩                     209.7 MB   disk0s1
   2:                 Apple_APFS ⁨Container disk1⁩         250.8 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +250.8 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume ⁨SSD - Data⁩              154.4 GB   disk1s1
   2:                APFS Volume ⁨Preboot⁩                 443.8 MB   disk1s2
   3:                APFS Volume ⁨Recovery⁩                623.4 MB   disk1s3
   4:                APFS Volume ⁨VM⁩                      3.2 GB     disk1s4
   5:                APFS Volume ⁨SSD⁩                     15.3 GB    disk1s5
   6:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.3 GB    disk1s5s1
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  • Since the dawn of (computer) time hard drives have been less than the advertised capacity. I believe most of it is how manufacturers measure bytes. For RAM 1 GB is 1024Mb (mega bits) for drives (SSD & mechanical) 1GB is 1000Mb. In addition to that there is the headroom that the file system uses and there is the space reserved by the drive itself so it can map out bad blocks and other housekeeping chores. And different manufacturers drives will very in what is user space and what is taken up by formatting, bad block remapping and general housekeeping. Commented Nov 11, 2021 at 11:20
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    Can you add to your question, the results in txt mode of the two commandes : system_profiler SPNVMeDataTypeand diskutil list
    – user415185
    Commented Nov 11, 2021 at 11:26
  • Just to add to the confusion, storage & RAM chips are manufactured in binary units but measured in decimal; the formatting itself takes up some 'space' & the provisioning some more. In the end, 5GB off the top end of 500 is really neither here nor there. It's not space you should even contemplate using, you should always keep 10-15% free space anyway. See en.wikipedia.org/wiki/Gigabyte#Consumer_confusion for some back-story.
    – Tetsujin
    Commented Nov 11, 2021 at 12:23
  • It’s not at all clear there is a difference you suspect so I’ll answer in general which is what I think you mean with the three questions asked at the end
    – bmike
    Commented Nov 11, 2021 at 12:49
  • Thanks for answers and comments. I have added outputs of system_profiler and diskutil list commands on both machines. It looks like the difference is caused by an additional recovery partition on the M1 machine. Commented Nov 11, 2021 at 14:14

1 Answer 1

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That amount of usable space difference you see reported is more likely caused by OS differences than hardware.

You can get much better results looking in the details of disk utility or diskutil or system_profiler on both physical disks. Your listing of diskutil list disk0 Is where to focus.

Lastly, note that 256 GB (gigabytes) is a software / decimal measure corresponding to 238.4 GiB (gibibytes) which is the hardware / binary measure.

SSD work differently than magnetic media in that the controller always has more storage built than the raw capacity since rather than marking blocks as bad, they ship over provisioned. This allows the storage controller to substitute groups of storage cells to balance wear leveling (reliability) needs with speed, durability and power consumption trade offs.

The main difference you should pay attention to is which storage controller is in play. Intel can have traditional storage or an Apple T2 chip. The Apple Silicon hardware uses a controller built into the SOC.

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  • Thank you. It looks like system_profiler and diskutil commands show a hidden recovery partition on the M1 machine. This partition does not exist on the Intel machine, and I don't know why.. Commented Nov 11, 2021 at 14:16
  • All modern macOS have hidden partitions. Nothing to do with the CPU. Great work. The disk0s1 and other items are where to focus. All yours are sized correctly on both systems
    – bmike
    Commented Nov 11, 2021 at 15:05

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