Which NAS Works Best With a Mac? Two Version Numbers

I went looking for which NAS works best with a Mac because I was close to buying one. Our blog and its automation run on a Mac mini that stays powered on, and its backup story is thin. Every article I found answered with a brand: a ranked list, a badge, an affiliate button.

Then I checked what my own Mac would do with a NAS before picking one, and the shopping question fell apart. In August 2026, the brand is not the deciding factor. Two version numbers are — one on the Mac, one on the NAS — and most vendors publish neither.

What my Mac says right now

Here is the machine that would be doing the backing up, measured today:

$ sysctl -n hw.model
Mac16,10

$ sw_vers
ProductVersion:  26.4.1
BuildVersion:    25E253

$ softwareupdate -l
* Label: macOS Tahoe 26.6.1-25G76
  Title: macOS Tahoe 26.6.1, Version: 26.6.1, Size: 4128766KiB,
  Recommended: YES, Action: restart

macOS 26.4.1. That number matters more than any NAS I could have bought, because 26.4 and 26.4.1 are the two releases carrying an Apple-side bug that breaks Time Machine to network storage. Cult of Mac reported it on 2026-03-31: the Mac writes the wrong server key into serverMarkers.plist, authentication to the NAS fails, and the logs show NAConnectToServerSync failed with error: 80. The brands named were Synology, UGREEN and TerraMaster — the bug does not care which you buy.

The fix shipped in 26.5. My machine has had 26.6.1 sitting in the update queue, flagged Recommended: YES, the whole time I was reading NAS comparisons. I was shopping for hardware to solve a problem an unapplied update on my own desk was creating.

Why the obvious test does not work

The test everyone runs in a store or a return window is: does it mount? That test cannot answer this question, and the reason is readable on any Mac.

The SMB client reads its defaults from nsmb.conf. There is no such file on my machine — neither /etc/nsmb.conf nor ~/Library/Preferences/nsmb.conf exists — so the documented defaults from man 5 nsmb.conf are what is in force. Two of them matter:

Key	Default	What the man page says it means
protocol_vers_map	7	7 == 0111 — SMB 1/2/3 should be enabled
signing_req_vers	6	Signing required for SMB 2/3
signing_required	no	Turn on smb client signing

SMB 1 is still enabled on the client by default in macOS 26.4. So a cheap box speaking an ancient dialect will mount, appear in Finder, and copy files. Mounting proves almost nothing.

Time Machine asks for far more. Apple's Time Machine Over SMB Specification requires the server to do six things: SMB 3.x including SMB 3.x signing; handle SMB2_CREATE_DURABLE_HANDLE_REQUEST_V2 and honor its Timeout field; handle SMB2_CREATE_REQUEST_LEASE_V2; handle SMB2_CREATE_DURABLE_HANDLE_RECONNECT_V2; advertise _smb._tcp on port 445 plus _adisk._tcp with a TXT record carrying adVF=0x82; and support F_FULLFSYNC, an SMB2 FLUSH with Reserved1 = 0xFFFF that must reach stable storage, advertised through the AAPL create context as kAAPL_SUPPORTS_FULL_SYNC.

Four of those six will never appear on a spec sheet, and they are exactly what fails after the mount succeeds. In the Apple thread on Tahoe 26.2 and Synology, opened 2026-01-19, users mount and authenticate fine, then hit Failed to read capabilities for /Volumes/... Operation not permitted (NSPOSIXErrorDomain Code 13) and TMDisk attrVolumeWithMountPoint failed (Permission denied). The same thread records what stopped being an escape hatch: NFS returns error 45, and AFP is no longer supported for new backups on Tahoe.

The second number: which Samba the NAS runs

Nearly every consumer NAS serves SMB with Samba, and one Samba release broke Time Machine for all of them. Samba bug 15926, titled "Samba 4.22 breaks Time Machine", was opened by Ralph Böhme on 2025-10-02 and is resolved fixed. The cause was not a security tightening. The fruit:posix_rename option was removed in 4.22 because, in the bug's words, it "imposed an unreasonable development burden due to introducing hard to follow logic in very complex code."

Time Machine renames a directory while a file inside it is still open — it creates the sparsebundle under the filesystem UUID and renames it to the machine name, and uses the same call when adding band files to grow a backup. So the breakage is not limited to setup. An existing, working backup fails later, at the unpredictable moment it needs more space. The fix landed in Samba 4.22.6 on 2025-10-16.

A higher version number is not automatically safer

The advice circulating in forums is "get Samba 4.22.6 or newer, or anything on 4.23." The bug's own comment thread contradicts the second half. A February 2026 comment on bug 15926 states: "I believe this is only fixed in the 4.22.x branch; it's still an issue with the latest 4.23 releases, including 4.23.5." The commenter reports 4.22.8 working and 4.23.5 failing.

So the ordering inverts: 4.22.8 is a safer target than 4.23.5. I have not reproduced this — it rests on one comment — but it is the primary record, and it contradicts the secondary write-ups.

Those write-ups get two other things wrong, worth naming because they are what a shopper finds first. Several attribute the NAS-side breakage to stricter SMB signing in Tahoe; the Samba record says the cause was the fruit:posix_rename removal, a rename behavior change. And several give the affected range as "4.21 through 4.22.3"; since the removal landed in 4.22, 4.21 is not affected at all — TrueNAS shipped 25.10.0 on Samba 4.21.7 and 4.21.9 without it.

Who actually tells you the number

If the Samba version decides whether your Mac can back up, the practical question is whether you can find it out before paying. On 2026-08-17 I checked the public documentation of six NAS platforms for that one number.

Platform	Publishes its Samba version?	What the docs actually say
Synology DSM 7.3	No	The spec page says it supports SMB1, SMB2, SMB3 encryption and Time Machine on macOS 10.12 and later. No Samba version anywhere.
QNAP QTS	A table, three years stale	An official FAQ maps QTS to Samba, but was last modified 2023-04-11 and stops at QTS 5.1.x / Samba 4.15.0. No QuTS hero rows.
TerraMaster TOS 6	No	Documents a minimum and maximum SMB dialect selector. No Samba version.
UGREEN UGOS Pro	No	Publishes a Mac and Time Machine setup guide. No Samba version.
TrueNAS SCALE 25.10	Yes, with the reason	Version notes: "Updates Samba from 4.22.5 to 4.22.6" and "Resolves an issue where Time Machine backups failed ... due to a Samba 4.22 behavioral change affecting directory rename operations for open files."
Umbrel	Yes, in public	The bundled version is discussed openly in issue 2094, opened 2026-01-13, which reports the sparsebundle being created and then failing immediately.

The pattern is uncomfortable for a shopping list. The platforms that publish the deciding number are the do-it-yourself ones. The appliance vendors that advertise Time Machine support on the box mostly do not, and the one appliance vendor that published a table let it go stale at a Samba version seven releases below the threshold that now matters.

What I would check instead of a brand ranking

All of this is checkable with tools already on your Mac, most of it inside a return window:

1. sw_vers — if you are on 26.4 or 26.4.1, fix that first. No purchase helps.
2. dns-sd -t 6 -B _adisk._tcp local — if the NAS does not advertise this service, Time Machine will not offer it as a destination. On my network this returns nothing, because I do not own a NAS.
3. smbutil statshares -a after mounting — shows the dialect actually negotiated, not the one advertised.
4. On the NAS over SSH, smbd -V — the number the brochure omits. Avoid 4.22.0 through 4.22.5.
5. Watch backupd in Console for Failed to read capabilities or NAConnectToServerSync failed with error: 80. Those are capability and credential failures, not disk problems.

So which NAS works best with a Mac

The honest answer for August 2026 is that the box is the least decisive part of the purchase. Buy for the things a firmware update cannot change — bays, RAM ceiling, network speed — then verify the SMB behavior in the return window.

On the two units I priced while researching this, neither of which I own: the UGREEN NASync DXP2800 is specified by the manufacturer as an Intel N100 with 8 GB DDR5 expandable to 16 GB, two bays plus two M.2 NVMe slots and 2.5GbE, listed at $389.99 on sale against $439.99 regular on UGREEN's own site as of 2026-08-11. That 16 GB ceiling is not a UGREEN decision but the Intel N-series platform limit, the product page publishes no idle power draw, and UGREEN is one of the three brands named in the 26.4 bug reports. The Synology DS425+ is specified at 2 GB RAM installed with a 6 GB maximum; Synology's capability failures dominate the Apple thread above, and its 2025 drive-compatibility restrictions drew a 1,037-point Hacker News thread before being partly walked back.

If knowing what your server runs matters to you, the audit points somewhere specific: the platforms that told me their Samba version are the ones you assemble yourself. That is the same trade we weighed when we compared building a Mac mini server against buying a NAS. Before committing, it is worth reading why Time Machine to a NAS is a latency problem rather than a bandwidth one, how to tell CMR drives from SMR before filling the bays, and whether you need a switch for your home network to feed it.

Affiliate disclosure: the UGREEN link above is an Amazon Associates link and pays us a commission if you buy; it costs you nothing extra and does not change what is written here. On sourcing: the measurements of my own machine — macOS 26.4.1 build 25E253, the pending 26.6.1 update, the absent nsmb.conf files, the empty _adisk._tcp browse — were taken on 2026-08-17 on a Mac16,10. I do not own a NAS, so the empty Bonjour result reflects an absent device, not a failing one, and I have not reproduced either bug myself; what I verified is that my machine sits on the affected macOS version. The Samba behavior comes from bug 15926 and the 4.22.6 release notes; the claim that 4.23.5 still fails rests on a single February 2026 comment there that I did not test. The vendor disclosure audit covered six platforms' public documentation on 2026-08-17 only — I did not SSH into any of these devices to read smbd -V. Product specifications and prices are the manufacturers' own figures, checked 2026-08-11, and Amazon's price was not machine-readable so none is quoted. One user in the Apple thread reports Time Machine working normally on a DS223j under 26.2, so these failures are not uniform across configurations. The openmediavault forum thread and taoofmac post on this topic both returned HTTP 403 to me and are not cited. I have not yet applied 26.6.1 to the server.