I recently purchased a DS517 to expand my DS1817+ Raid. I went through all the steps on the Synology side to increase the volume size. However, my Mac OS computer is still showing the old size of 53.7 TB instead of the new size of 92.8 TB.

When I try to use Disk Utility and go through the Partition tab. I can select the "Free Space" and click the "-" sign, and it shows the projected new space of 92.8 TB. When I click "Apply" it gives me the error of:

"The new size must be different than the existing size."

In Terminal, when I run "diskutil list" I can see the new size, but the container it's in is the old size. It shows -

/dev/disk4 (external):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         92.8 TB    disk4
   1:                        EFI EFI                     209.7 MB   disk4s1
   2:                 Apple_APFS Container disk5         53.7 TB    disk4s2

/dev/disk5 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +53.7 TB    disk5
                                 Physical Store disk4s2
   1:                APFS Volume CC-SYN1                 52.6 TB    disk5s1

I've found commands such as diskutil apfs resizeContainer disk4s2 0 that supposedly are supposed to fix it, but it gives me the error of:

Error: -69743: The new size must be different than the existing size

I don't have a spare 54 TB raid sitting somewhere to where I can just format and start over, so I'm hoping there's a way to get the container to show the new size. It's obviously there, but after searching Google for hours and seeing mostly the same "solutions" without it working, I'm not sure what else to do/try.

  • I'm voting to close this question as off-topic because this is not about Apple hardware, software, or services as defined in the Help Center – Allan Mar 15 at 18:29
  • @Allan - "third-party hardware, services and software when associated for use with Apple products" is listed in the Help Center as a type of question I can ask. Since it was dealing with a third-party hardware (Synology) for use with APFS (an Apple file system) on how to have it recognized in Mac OS X after expanding, since the container was showing the old size. – Damian Cardona Mar 15 at 19:23
  • The Synology is a self contained unit and the issue is not with Apple, but with Synology. If you had a Microsoft Surface, the problem would have been exactly the same. – Allan Mar 15 at 19:27
  • The fix was issued in Terminal due to the APFS container not recognizing the expanded size. It was not a fix on the Synology side, and did not touch anything Synology-wise that remedied the problem. It was APFS. – Damian Cardona Mar 15 at 19:33

I figured this out a few days after posting my question, and figured I should followup for anyone else experiencing a similar problem. I came across gdisk and used the following instructions in Terminal to fix the issue:

* Type "sudo gdisk /dev/sdc" (or whatever the appropriate device filename is)
* Type "x" to enter experts' mode
* Type "e" to relocate the backup data
* Type "w" to save your changes.
  • Where would one enter these commands? I would imagine on the Synology since /dev/sdc aren't macOS device identifiers, but Linux ones. – Allan Mar 15 at 19:06
  • @Allan - Terminal inside Mac OS X. I updated post to mention Terminal. – Damian Cardona Mar 15 at 19:24
  • By starting an ssh connection to the Synology, right? macOS doesn't use the gdisk utility or use /dev/sdc as identifiers. – Allan Mar 15 at 19:28
  • No. It was just a Terminal command, after installing gdisk. – Damian Cardona Mar 15 at 19:35
  • @Allan This is clearly a macOS problem - not a Synology problem. You have misunderstood this. Damian is entirely correct that this is a macOS problem, and he has the right solution for it. The mac needs to move the backup of the data structure to the end of the disk, thus opening up the room for APFS to enlarge the container. That was not possible before because that backup was "stuck in the middle". – jksoegaard Mar 15 at 22:23

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