Disk access issues - exFat and Samba

Let's go over each of the issues that you have brought up in your post.

exFAT drives not appearing on macOS

This is usually caused by one of three things:

• The drive isn’t getting enough power (very common with large-capacity externals).
• The exFAT file system has minor corruption from being used across platforms.
• The drive is being presented through a USB/SATA bridge macOS doesn’t fully like.

Some things you can try to resolve this:

• Connect the drives directly (no hubs) and use a powered enclosure if possible.
• Open Disk Utility → View “Show All Devices” and check if the disk appears but isn’t mounting.
  • If it shows but won’t mount, running a First Aid check from Disk Utility often restores access.
• Long-term, for Mac-heavy workflows, migrating to APFS (or exFAT only for transfer drives) improves reliability and speed.

Extremely slow Samba transfers

macOS Sequoia defaults to secure SMB settings that can hurt performance when talking to Linux servers. The slowdown you’re seeing is usually caused by SMB version mismatches, encryption overhead, or inefficient file copy methods for very large datasets.

Some things you can try to resolve this:

• Make sure the Linux server is using SMB3 and has signing/encryption set to “auto” rather than forced.
• Use a wired network connection whenever possible — Wi-Fi will bottleneck large transfers badly.
• For large jobs, tools like `rsync` or a copy utility that supports multi-threading will be dramatically faster than Finder alone.

No way to resume interrupted copies

Finder is convenient, but it’s not designed for enterprise-scale transfers. When a large job fails, it doesn’t handle resuming gracefully, which is why you’re forced into restarting file-by-file.

One thing you can try to resolve this:

Use a copy tool that supports verification and resume (rsync, ChronoSync, Carbon Copy Cloner, etc.). These tools only transfer what’s missing, so if a job stops halfway through, you simply restart it and it continues where it left off.

Concern about upgrading or reinstalling Sequoia on an external drive

You’re right — installing macOS to an external drive can be more complex than it should be, especially on Apple silicon. That said, staying on your current version won’t prevent you from fixing the storage and network issues you’re seeing now. Everything above works fully on the version of Sequoia you're using now, so there’s no immediate need to upgrade just to resolve these problems.

Concerning your ExFAT drives, it would help if you identify the exact make & model of each "bay" and each drive ... including the version of USB each "bay" supports ... and if your USB cable(s) are up to the necessary spec. Also confirm you aren't using any USB plug adapters; whether or not you are daisy-chaining any of the drives; and exactly which USB ports you are using on the M4 mini (the front & back ports are different). All these things can affect drive connectivity.

Also, ExFAT isn't journaled and as such it is prone to corruption if not properly ejected before pulling the cable. With an ExFAT drive, I would *never* unplug the drive unless the computer is powered off first.

What is your backup situation?

robbie_moose wrote:

The drives are in powered bays, straight into the Mac on USB. They sadly aren't appearing on Disk Utility.

Perhaps the problem is the bays. Maybe check "diskutil list" on the command line. That's more likely to show all physical devices, whether or not they are mounted and/or readable. If they don't show up in "diskutil list", then it's definitely the bays.

Yer_Man: My apps total 446GB and for anything bigger than 256GB Apple's disk prices are insane. It's an off-the-shelf Mac Mini M4, though has 32GB RAM.

But it's insanely fast too. You paid for that speed, but you're not using it. If the only limitation is your apps, you can move those to any visible volume. If you can run the OS from the internal SSD, that should result in a noticeable performance boost.

robbie_moose wrote:

I'm reasonably new to MacOS, and have a couple of questions that I hope someone can help me with.

I'm running 15.4.1 Sequoia from an external drive on an M4 Mac, doing a lot of data-intensive video work.

I'm very reluctant to upgrade from Sequoia as installation to an external drive is something of an ordeal as MacOS doesn't seem to want to do it.

FYI, make sure your external boot drive is not connected to the DFU port when updating or upgrading macOS. See the following Apple article for details:

How to use an external storage device as a Mac startup disk - Apple Support

Although I despise Windows, at least I could access my data in a reliable and timely manner; I'm starting to wonder whether switching to Apple was such a good idea...

Macs are much more picky about the devices being connected whereas Windows tends to be more forgiving & tends to be better able to deal with the unexpected.

Keep in mind third party device manufacturers cater more towards Windows....every thing else is just luck so it is best to use external devices that are of good reliable quality that is known to work with other platforms. Software developers also mostly cater to Windows even when they provide a macOS native version (the macOS version of the app will usually not be optimized to take advantage of macOS features in order for the developer to utilize the same codebase with fewer changes between platforms).

even trying to post this question here resulted in a '429 too many requests' error. Grrrrrr!

Yeah, Apple's Discussion forums have been experiencing a lot of problems these past few weeks. It has been extremely rough & painful for the forum contributors as well.

@Tesserax has you well covered on the other points & questions.

Some data for storage access and remote file server access 1000BASE-X (GbE) is 1 Gbps, 2.5GBASE-T (2.5 GbE) is 2.5 Gbps, IEEE 802.11ax (Wi-Fi 6E) tops out at 11 Gbps, while even the comparatively old storage buses run faster with PCIe 1.0 x1 at 2.5 Gbps, and a Mac mini M4 with 512 or more GB offers Thunderbolt 4 at 40 Gbps write and 35 Gbps read.

Network file access here is theoretical, and ignoring file server overhead, and ignores whatever server storage hardware speeds might further constrain performance.

As for hard disk drives, those are just spectacularly slow: Why is my hard disk drive iMac so slow? - Apple Community A fast HDD does ~150 to ~200 I/O operations per second. A slow SSD does ~100,000 I/O operations per second.

If you’re really using HDDs, and you want storage I/O speed, you don’t want HDDs.

USB is another area where performance can range from slow to less slow to decently speedy, but that is based on which USB version is in use on both ends of the USB cable, and on USB configuration subtleties such as (unwisely) using charging cables netting you USB 2.0 (glacial) speeds.

ExFAT isn’t a great choice for a file system, either.

Various higher-spec NAS boxes include off-site backups and/or replication.

Ubiquiti UNAS offers off-site backups, and Synology DSM off-site backups and replication. Both offer remote access, as well. There are other good NAS options here, including TrueNAS.

The NAS Compare website and Youtube channel offers a wealth of well-presented NAS and related networking info, if you want a wider view of what is available and how well it works.

PS: if you’re dealing with macOS and NAS, you very likely want a NAS with Time Machine server capabilities.

• Time Machine Over SMB Specification
• https://kb.synology.com/en-global/DSM/tutorial/How_to_back_up_files_from_Mac_to_Synology_NAS_with_Time_Machine
• etc.

What type of SSD is your external, what type of enclosure is it and how connected to your Mini.

For comparison what are your read and write speeds to your boot drive using Blackmagic Disc Speed Test app (free).

I have the base (10 core) Mac Mini M4 with a 1 TB boot drive. My read and write speeds are: Write - 2723 Mbs and Read - 2858 Mbs. It's down from its new reading of Write-3036 and Write-2900 Mbs as it gets filled up. I have the Stress level set to 5 GB.

What are your's?

Try run the OS from the Machine and put your apps on the external.

robbie_moose wrote:

I fear you (Tesserax) are right about minor corruption - possibly due to being 'hot removed'. There's no way I'm moving all these over to APFS though as it'd take forever, and I need read/write access across different platforms.

Are you aware of any other way to fix the minor corruption?

Here I concur with etresoft about the drive bays and how to do a quick check via diskutil. Curious, what are the make & model of these bays?

robbie_moose wrote:

Just one quick question though: why does this forum post replies seemingly at random? It's really hard to read a thread consecutively.

• Log into the Communities, as you have been doing.
• Once logged in, click your avatar icon in the upper right of a Communities window.
• Select Preferences.
• Scroll down to Other Preferences
• Set Default Thread Sort = Oldest
• Click Submit

Posts will then appear in date/time order whenever you are logged in.

robbie_moose wrote:

MrHoffman - which format would you suggest for a disk that needs to be accessed by a range of different Operating Systems?]

If pushing lots of bits, SMB via 5 GbE or 10 GbE or maybe Fibre Channel for shared access, with HFS+ or APFS if served via macOS, NTFS from Windows, ZFS, btrfs, or ext4 served from Linux, and btrfs or ext4 from Synology NAS. Ubiquiti doesn’t even document what they use for UNAS models, AFAICT.

If hardware RAID is involved, usually RAID-6 or RAID-10, and definitely not RAID-5. Absolutely not RAID-5. Nope.

For storage technology HDD or HDD with NVMe cache for price, and SSD or NVMe for performance.

Tangled nests of USB cables to randomly-selected USB storage devices are very low on my preferences, preferring Thunderbolt shelves for lots of direct local storage or for Mac-served NAS storage, this using shelves such as Promise Pegasus. Or for dedicated sharing, NAS boxes from Ubiquiti, Synology, UGREEN or such. Nests of USB cables tend to get flaky.

Various NAS devices can provide other network services, as well.

See the NAS Compares website and their Youtube channel for NAS info.

Just one quick question though: why does this forum post replies seemingly at random? It's really hard to read a thread consecutively.

Set thread order chronological (locally “oldest”) rather than random (“upvotes”, or previously listed as “best”):

Or set default profile order (locally “oldest”) to chronological and not random (“upvotes, formerly “best”):

To access your forum profile settings and preferences, tap the circular icon in the upper right corner.