Exfat formated USB SMB-Drive (Synolgy NAS 124) for Timemachine backup in Tahoe

Hi,

You cannot use an exFAT-formatted USB drive connected to a Synology NAS for Time Machine backups, because Time Machine requires a native file system like ext4 or Btrfs for attached USB drives on a Synology system, or an APFS structure when used locally.

Why exFAT Fails for Time Machine

• File System Incompatibility: macOS and Time Machine require specific file attributes, hard links, and permission handling (POSIX/ACLs) that exFAT does not support.
• Synology Limitations: When formatting external USB drives directly on a Synology NAS, Synology explicitly requires ext4 or Btrfs for Time Machine targets.
• macOS Tahoe Network Quirks: macOS Tahoe introduces stricter SMB handling and capability checks. Even if shared over SMB, an underlying exFAT volume will reject sparse-bundle image creation or fail capability validation.

Recommended Solution

1. Reformat the USB Drive: Log into your Synology DSM, go to Control Panel > External Devices, and reformat the USB drive to Btrfs (or ext4 if Btrfs is unavailable on your specific model).
2. Configure via SMB Properly: Instead of sharing the raw USB mount directly via an ad-hoc exFAT structure, set up a dedicated shared folder on a healthy internal NAS volume (or properly mapped external Btrfs/ext4 drive) and enable the official "Enable Time Machine" flag in Synology's file services.
3. Check ASCII Naming: Ensure your computer name and network share paths do not contain special accents or non-ASCII characters, which frequently trigger permission or "disk not found" errors in Tahoe.

Alfi wrote:

on synology i AFP and Exfat was the first i got to work while SMB failed unless i chose ext4 .

I have no idea why you would choose ExFAT, that's a Windows drive format. The DiskStation Manager (DSM) software that runs a Synology NAS is on Linux, and ext4 and Btrfs are native Linux drive formats. Synology recommends Btrfs, which is based on ext4 but supports checksums and snapshots.

Personally, I followed Synology's setup instructions (including formatting as the drives as Btrfs and using SMB3), and my TM backups and general file sharing for five Macs in the house have been running for years with no issues.

I kept AFP because i wouldnt have had any network backup as long SMB didnt work. Why should nobody use AFP? its really easy , especially with AEBS.

You should have been using SMB all along. AFP is now fully deprecated. Unless you never upgrade compatible Macs to Golden Gate and never buy a new Mac, if you're using AFP then inevitably your server/TM backup will stop working. SMB is really easy, too.

yes on the airportextr. I use HFS+ and AFP

on synology i AFP and Exfat was the first i got to work while SMB failed unless i chose ext4 . I kept AFP because i wouldnt have had any network backup as long SMB didnt work. Why should nobody use AFP? its really easy , especially with AEBS.

Be aware that Apple Filing Protocol (AFP) is a deprecated format for networking, and while that format works with macOS 26 Tahoe, the format will no longer be supported by Apple starting with macOS 27. It was deprecated on the server side with Big Sur (6 years ago), and client side support is now over.

You are really best off following Synology's instructions for standing up TM backups to their NAS (setup instructions). Using deprecated formats and unsupported drive formats is going to cause problems, and Murphy's Law says those problems will happen right when you most need the TM backup.

At the moment, I’m running SMB and AFP simultaneously even on the new Mac for sure and have redundancy. And the reason why I use exfat because it can be read natively on the Mac while Btrfs ext4 cannot be read by the Mac natively. With SMB everything has become more complicated and because maybe reason is that reason Apple has stopped to produce own routers and doesn’t support AEBS any more. There are some attempts to get SMB work on AEBS in a special project. And at the moment, SMB is recommended by Apple, but I see I people which are really specialist on Mac and have troubles to get it to work. Which they never experienced with AFP. So I don’t see any reason not to use this with older system

Alfi wrote:

And why I did it? : I can natively format and read it with Mac and this is important when the NAS does not work.

I can see the desire for that, but personally it doesn't concern me. Two options if that happens – mount the drive(s) via a micro-VM (there is a GitHub script that allows command-line mounting of a btrfs-formatted drive), or if the NAS actually fails just buy a new one and move the drives over. I had to do that with a QNAP NAS (before I switched to Synology), it works fine.

and so I still am working to find another way to do the back up on a [drive] that can be red natively by the Mac OS

You can use an attached external drive formatted as APFS for backups, instead. Personally, I use both. I follow the commonly recommended strategy of 3-2-1, where you have (at least) three copies of your data, two of which are backups and one of which is stored offsite. I back up the Macs in the house to the NAS hourly (which is actually two copies since it's a 2-bay enclosure in RAID 1), and back them up weekly to a pair of large SSDs, swapping one of them offsite (to the desk in my office). The data on the general file share volume of the NAS are also backed up to a pair of SSDs.

Yes thank you thats how I had got to work. I was hoping to Find a work around as on the Same NAS it’s working

with exfat and Time Machine but with AFP only. And with SMB with ext4 . These two TIMEMACHINE backups run from the same computer to the same NAS. And they both work.

Thank you, I know that,.... that is why I switched to SMB before AFP stops working. . Everyone using Time Machine with AFP gets the warning in the interface of Time Machine that AFP will not work with macOS 27 and SMB disk is recommended. AFP is working fine on one of my a Macs using Ventura which is even newer than Big Sur.

Alfi wrote:

AFP is working fine on one of my a Macs using Ventura which is even newer than Big Sur.

Yes – server side and client side are not the same thing. 'Deprecated on the server side in Big Sur' (as I stated) means that you cannot set up an AFP server on a Mac running Big Sur or later. The client side (your Mac accessing an AFP server) was fully deprecated in macOS 27 Golden Gate, up through Tahoe you could still connect to a server running AFP.

The default networking protocol was changed from AFP to SMB in OS X Mavericks (2013). The writing has been on the wall for AFP for a long time.

By default, the AirPort Extreme Base Station used AFP for the network connection to an external drive if that drive was formatted as HFS+ (MacOS Extended), and it used SMB if the drive was formatted as FAT (for Windows). Presumably, you formatted the drive on you Mac at the time, so it would have been HFS+ and the AEBS would have used AFP (that's the 'server side') . Support for Samba on the AEBS was limited to the old SMB v1 protocol, so that would not work today for Time Machine anyway, because TM now requires at least SMB v2 (SMB v3 is recommended).

Synology still supports AFP, but nobody should be using it.

i’m not going to use an internal drive, because it would be Dr. I can attach as many drives as I want even if the NAS can hold only a single internal drive . and I use one physical drive for only one computer I never back up more than one computer to a physical drive.

And why I did it? : I can natively format and read it with Mac and this is important when the NAS does not work. and there was no direct hint that you must not use it.

and so I still am working to find another way to do the back up on a woman that can be red natively by the Mac OS

Alfi wrote:

Does the github Skript allow to use Time Machine Back-up by migration assistant? I know I have to set up the computer first, run the script and maybe the assistant sees it too?

Sorry, I do not know if that would work. If I need to use a TM backup restore a Mac (which I've never had to do) or set up a replacement Mac (which I've had to do many times), I use a fresh backup on one of my SSDs. Setting up a new MBP with ~700 GB of data to be migrated took 20-25 minutes, with a spinning HDD that would have taken hours.

Thank you this i interesting.. I never set up a server on my computers , I was always using AEBS with USB drive attached to it.This is the first time i bought a NAS- because of these changes

Does the github Skript allow to use Time Machine Back-up by migration assistant? I know I have to set up the computer first, run the script and maybe the assistant sees it too?

true , thats how i did it too. Even with this concerned computer.i never had a complete crash( luckily)so far