Time Machine not discovering successfully mapped SMB share from my WD My Cloud Mirror

Given the age of the hardware, issues are not a big surprise. There was a post earlier today from a user with TM backups not working on two external drives...turned out one was a FireWire drive and the other was a Time Capsule, both of which are now deprecated.

Why Time Machine Fails to See the Share

• Missing Bonjour/Time Machine Advertising: Modern Time Machine relies on specific network discovery flags that old OS3 firmware does not broadcast over SMB. 
• Unsupported Protocol Handshake: Western Digital OS3 uses an older implementation of Samba that does not identify itself to newer macOS versions as a valid Time Machine backup target.

Some users have reported success on an older WD mapped share with the following workaround, though it's not clear if this will work on macOS 27.

Mount the SMB Share

• Connect to your WD My Cloud Mirror share in Finder using smb:// and make sure you log in with your NAS user credentials. 

Create a Sparse Bundle Disk Image

• Open Disk Utility on your Mac.
• Go to File > New Image > Blank Image.
• Set the Save As name to something recognizable (e.g., MacBackup).
• Set the Where location to the mounted SMB share folder on your WD My Cloud.
• Set the Size to your desired backup limit (e.g., 500 GB or 1 TB).
• Set Format to APFS or Mac OS Extended (Journaled).
• Set Partitions to GUID Partition Map.
• Set Image Format to sparsebundle disk image (this is critical so the backup can grow dynamically). Click Save.

Mount the Sparse Bundle

• In Finder, navigate to your SMB share and double-click the newly created .sparsebundle file to mount it on your Mac.

Assign the Sparse Bundle to Time Machine via Terminal

• Give your Terminal app Full Disk Access in System Settings > Privacy & Security > Full Disk Access.
• Open Terminal and run the following command (replace /Volumes/MacBackup with the actual name of your mounted sparse bundle volume):

sudo tmutil setdestination /Volumes/MacBackup

• Enter your Mac administrator password when prompted (nothing will show as you type).

Start the Backup

• Open Time Machine in System Settings and trigger a manual backup (Back Up Now). Time Machine will write the backup data inside the mounted sparse bundle over SMB

Apple's advice on TM troubleshooting:

Time Machine troubleshooting on Mac - Apple Support

If Time Machine on your Mac can’t find your backup disk - Apple Support

Options? Replace the My Cloud Mirror OS 3 gear, given the age, the lack of support and upgrades, and the known security issues. Pick something with Time Machine Server support.

Otherwise, see if mDNS is reporting any related network-connected storage from the Terminal app command line:

dns-sd -B  _adisk._tcp.

Which returns something like this, here edited to remove info:

Browsing for _adisk._tcp.
DATE: ---Tue 27 Oct 2026---
22:19:26.551  ...STARTING...
Timestamp     A/R    Flags  if Domain               Service Type         Instance Name
hh:mm:ss.552  Add        3  21 local.               _adisk._tcp.         nasbox1
hh:mm:ss.552  Add        3  18 local.               _adisk._tcp.         nasbox1

There are other tools for this mDNS stuff, though those are add-ons and the ones I use are not free.

Then check whether SMB 3.x is supported. The following assumes the NAS storage is already mounted using SMB, and the sudo shown requires an admin password:

sudo smbutil statshares -a

Then look for this line in the wad of output:

 SMB_VERSION                   SMB_3.1.1

Quacks wrote:

Thank you.

For the 2nd part, I got....

SMB_VERSION                   SMB_3.0

For the 1st part, it is taking forever. Should it take a long time to complete? Not much is on my network. I have tried over wireless and Ethernet. Also, should I have one of the Shares mounted or not?

The command listens until stopped. Use ^C to stop. For syntax details, a non-AI search engine, as well as man dns-sd or such, and maybe a zsh guide.

With no mDNS, your NAS doesn’t support Time Machine server.

That means Time Machine can’t find the storage.

Which is what the WD My Cloud Mirror support folks were unfamiliar with.

Whether you can find a hack-around to bypass a lack of mDNS on an unsupported NAS (as described in another reply), or build something that multicasts the necessary mDNS as a proxy for this NAS, donno. Feasible, but work.

For technical and implementation details, look for existing discussions of mDNS, and of _adisk._tcp and _smb._tcp, and particularly at the Apple Time Machine server info:

• Time Machine Over SMB Specification
• Time Machine and Time Capsule replacement - Apple Community (includes alternatives)

Or switch to something else with Time Machine server support. UGREEN, probably. Synology DSM and Ubiquiti UniFi UNAS definitely, current versions of Samba, or on zimaOS or whatever NAS OS definitely, etc.

But I’m also not usually running so-called bleeding edge major new versions either, absent specific requirements.

I used the term “hack-around” and not “work-around”, and specifically indicated (“donno”) I didn’t know if that’d work: “Whether you can find a hack-around to bypass a lack of mDNS on an unsupported NAS (as described in another reply), or build something that multicasts the necessary mDNS as a proxy for this NAS, donno.”

My version of “Feasible, but work”: I can get an mDNS server working with gear I have available and can program it to adapt to the configuration details and then transmit the necessary mDNS entries, but already have access to NAS boxes with Time Machine server support. Probably possible to get an app to do this and not a separate server, but haven’t looked.

If you want to play with old and unsupported gear, you’re going to get to learn much more about it, and how it does and doesn’t work.

There are some open-source tools related to this series of NAS boxes, but am not inclined to invest a few hours poking around at this. And there are undoubtedly forums more focused on NAS gear, too.

But using that same available or equivalent “surplus” gear as available foe mDNS shenanigans, I can probably also get ZimaOS working and migrate he Time Machine storage to that box.

Getting a couple of USB sleds will be the cheapest and most direct, assuming disassembly is an option, and assuming there’s not something weird about the SATA HDDs here. Otherwise, figure out if there is open source for the box, or figure out how to host those HDDDs else-box, or get an mDNS server going somewhere and code that to report the IP address and storage info of the WD NAS box.

The problem with old gear in IT: lots of stuff is possible, given sufficient time and money and skills.

Going price for a new 4 to 6 TB external HDD looks to be around USD$200. These days, I can blow through that in parts purchases pretty easily.

Thank you.

For the 2nd part, I got....

SMB_VERSION                   SMB_3.0

For the 1st part, it is taking forever. Should it take a long time to complete? Not much is on my network. I have tried over wireless and Ethernet. Also, should I have one of the Shares mounted or not?

Thank you... I should also mention that the WD Support people’s first steps were to send me 2 firmware bin files which supposedly would take care of this. Both failed when updating the firmware manually.

I prefer to fix the NAS and/or use a work around, but if I can't... rather than replace my NAS, is there an enclosure I can get for the disks (probably single disk enclosure), in order to back up to. I connect to UBC on my M2 MacBook Air, or I have an adapter to connect USB to UBC. I bought my Satachi adapter at the Apple store, as well as the ethernet adapter, when I got my Mac.

I would appreciate your recommendations for an enclosure? The NAS contains, 2 WD Red 3.5-inch SATA hard drives (2T each). WD checked the health of them and all is good.

There are USB (to SATA) storage “sleds” available, among other options.

My previous replies listed some of the common commercial and option-source NAS options, and my previous link included a whole write-up on the whole Time Capsule and NAS topic. And with links to a whole pile of video and text reviews from somebody that does a good job at it, and pays far more attention to NAS than most. (And has a video with some cogent recommendations for scrounging hard disks in 2026.) All previously linked.

As for more specific NAS recommendations, that depends on details not yet in evidence. Capacity, experience, budget, interconnects, mounting, all factor into these choices. The various installs I deal with use a mix of NAS-attached arrays and direct-attached arrays, and individual hard disks for isolated systems.

Thank you for this...

I am attempting your work-around.

1. For the Sparse Bundle, should I encrypt this?
2. My Drive is 2 TB... if I set the Sparse Bundle to 2 TB, if there is no room, will it adjust for that? fyi.. there are other shares with files in them on my NAS, so I know this will never be able to reach 2 TB.

Yes, I stand corrected... 'hack-around' :)

With my very limited skills, and time already spent on this, I think I'm just going to look at your suggested cheaper option...USB sleds. The NAS is nice and convenient, but for me it’s not necessary.

Again, thank you for all your help.

Hi...

Followed all the steps for the work-around, and got this:

Usage: tmutil setdestination [-a]  mount_point

tmutil setdestination [-ap] smb://user[:pass]@host/share

Does this mean anything? I replaced /Volumes/MacBackup with my mounted SparseBundle Name only (the one with .sparsebundle at the end of it).

Then, when I tried to run a Time Machine back up, it could not find any volumes to mount. It says 'no available time machine destinations'