[OSX] Disk partitions and Disk io counters

[valh1996]

Platform

• OSX Mojave 10.14.4
• psutil 5.6.2

In addition, I have:

• An internal hard disk with my 256 GB pro macbook
• 256 Gb external hard disk drive (Samsung SSD)
  ===

Bug description
When I retrieve the partitions (psutil.disk_partitions(all=False)), I get the following:

{
  '/dev/disk1s1': {'total': 250685575168, 'mountpoint': '/', 'fstype': 'apfs', 'used': 198136061952, 'free': 
  47547224064, 'percent': 80.6}, 
  '/dev/disk1s4': {'total': 250685575168, 'mountpoint': '/private/var/vm', 'fstype': 'apfs', 'used': 
  4295323648, 'free': 47547224064, 'percent': 8.3},
   '/dev/disk2s1': {'total': 250047627264, 'mountpoint': '/Volumes/ssd-t5', 'fstype': 'exfat', 'used': 
  121564823552, 'free': 128482803712, 'percent': 48.6}
}

And when I want to calculate the I/O for each of the disks (psutil.disk_io_counters(perdisk=True)), here is the result:

{
  'disk0': {'read_count': 26593782, 'write_count': 179212515, 'read_bytes': 210576470016, 'write_bytes': 
  2045853970432, 'read_time': 5858808, 'write_time': 33352953},
  'disk2': {'read_count': 812, 'write_count': 310, 'read_bytes': 21601792, 'write_bytes': 4809728, 'read_time': 
  327, 'write_time': 92}
}

What I don't understand is that the I/Os give me the disk0 and the disk2, but what is the link with the partitions /dev/disk1s1 and /dev/disk1s4 ????

It seems that it returns the result returned by the df -H command:

Filesystem      Size   Used  Avail Capacity iused               ifree %iused  Mounted on
/dev/disk1s1    251G   198G    47G    81% 4299257 9223372036850476550    0%   /
/dev/disk1s4    251G   4.3G    47G     9%       4 9223372036854775803    0%   /private/var/vm
/dev/disk2s1    250G   122G   128G    49%  927466              980246   49%   /Volumes/ssd-t5

No disk0 appears so far!

Except if I run diskutil list :

MacBook-Pro:~ user$ diskutil list
/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         251.0 GB   disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         250.7 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +250.7 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD            198.4 GB   disk1s1
   2:                APFS Volume Preboot                 45.8 MB    disk1s2
   3:                APFS Volume Recovery                522.7 MB   disk1s3
   4:                APFS Volume VM                      4.3 GB     disk1s4

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *250.1 GB   disk2
   1:               Windows_NTFS ssd-t5                 250.1 GB   disk2s1

Am I the one who's doing it the wrong way? I would simply like to recover the I/O for each of the disks and inside each disk to have the list of partitions with the disk_usage of each mountpoint. Store it all in a dictionary. But the above concern blocks me in this process...

Best regards