Mac Mini M2 Time Machine Problems with External SSD using Acasis TBU405 and 4tb WD SN850x

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Mac Mini M2 Time Machine Problems with External SSD using Acasis TBU405 and 4tb WD SN850x

I have two identical Acasis TBU405 external M.2 NVME enclosures, each loaded with a 4tb WD SN850x. Both drives use the APFS Encrypted GUID format.

I use one of these drives as a boot disk for my M2 Mac Mini Pro. Also, it contains all of my data.

The internal 1tb drive was too small when I upgraded: I had about 1.5tb of data on an internal SATA on my 2012 Mac Mini Quad Server, so I created a boot on that external 4tb drive when I bought the M2 Mini. The internal 1tb drive in the new M2 is not used (in fact, when prompted for the password to enable access to the internal data volume I hit "cancel" so that the internal drive is not used at all).

The other Acasis TBU405 with 4tb WD SN850x is called "Time Machine" and is a single volume, used only as my Time Machine backup drive.

However, since day 1, I noticed that my M2 Mini would almost always take several minutes to wake up, and report a Kernel Panic. This occurred on a daily basis.

And I also noticed that the Time Machine volume would often disappear from the Finder, and I often got the message "Disk Not Ejected Properly. Eject 'Time Machine' before turning it off." Whenever this happened, the green light on the Acasis enclosure was still on and the case felt hot (even a long time after disconnecting itself).

I did swap 4k Thunderbolt cables between the enclosures and bought several new ones, assuming faulty cables.

At the behest of Acasis tech support, I finally swapped cases: I opened both enclosures and swapped the Time Machine WD SSD and the Boot/Data Disk WD SSD so they were in opposite Acasis enclosures.

Interestingly, the Time Machine continued to improperly eject on its own and disappear from the finder while the boot SSD worked fine.

On a reboot Time Machine would reappear as it had in the other enclosure, until two or three instances later, it didn't reappear on a reboot: and from then on I couldn't get that volume to appear using any cable or enclosure. The WD SN850x SSD used for backups was fried.

So two weeks ago I sent that drive in for replacement under the warranty, and I just got the brand new WD SN850x yesterday. I excitedly put it into the enclosure, formatted it, designated it as the Time Machine backup destination drive and began the first backup (ETA almost exactly one hour for about 1.5tb). About 45 minutes into the first backup, the drive disconnected and the backup failed. I erased and tried it again, and once again it failed.

Instead of using the Thunderbolt 4 port on the Mini, I attached a USB-A to USB-C cable to the Time Machine drive and left it backing up overnight. That seems to work fine.

I suspect the enclosure and SSD combination just gets too hot and fries the card. But if anybody has any insight: please let me know.

I did turn off the energy saving feature "turn off hard drives when possible" but am afraid to re-connect the external enclosure to Thunderbolt 4 again and fry the card again.

Thank you.

Mac mini

Posted on Oct 11, 2023 9:32 PM

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Answer 1

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SalAlexander Author

Level 1

12 points

Oct 16, 2023 10:03 PM in response to woodmeister50

Today I got an email from Western Digital support about the WD SN850X:

The WD Black SN850X NVMe is intended for internal storage directly on the motherboard. WD does not recommend to use the drive on an external enclosures as it may cause connectivity or compatibility issue.

If you are looking for storage for Timemachine, we recommend you to use external HDD or SSD e.g., SanDisk Extreme Portable SSD or My Passport.

So: Don't use Acasis TBU405 with WD SN850X (and maybe don't use WD SSDs with any enclosure).

I have sent an inquiry to Samsung about compatibility with Samsung 990 Pro 4tb and post what I learn. Thank you everybody.

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Answer 2

SalAlexander Author

Level 1

12 points

Oct 24, 2023 7:30 PM in response to tbirdvet

I took the plunge, and got the Samsung 990 Pro 4tb NVMe SSD and so far: it works like a charm. I got through the first Time Machine backup (about 1.26TB) and have not had any disconnections or kernel panics in the week following woohooo!!!

I also found the YouTube video where the Acasis TBU405 in combination with the SN850X was recommended as the fastest, and warned them that it may be the fastest but that they are incompatible and shouldn't be trusted.

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Answer 3

Oct 12, 2023 5:46 AM in response to SalAlexander

I would think that the NVMe controller in the 850x would throttle speeds if the temperature gets too high as most SSDs will do. Perhaps there is a firmware update to the 850x? That is something I would check.

Is it possible that the thermal pad is a hair too thin and not making proper contact with the case to dissipate its heat?

Another possibility could be that the 850x is not quite compatible with the enclosure. DIY enclosure/SSD combos can sometimes be an adventure to find the exact paring (not just on Macs either). The Acasis site seems to mostly recommend the Samsung 980 Pro for their enclosures. While the site shows the WD 850 it doesn't show the 850x.

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Answer 4

SalAlexander Author

Level 1

12 points

Oct 12, 2023 9:03 AM in response to SalAlexander

The thermal pads have the indentation of the SSD card on them, and when opening the case I have to kind of pry the lid off because it is well stuck to the pads, so I am sure the pads are in full contact.

I did see some mentions of 850x firmware updates but would need to borrow a PC as the WD app that does firmware updates only runs on PCs. I will investigate this and report!

Also: I ordered a 10gbps enclosure since it was only 17 bucks shipped and like you mentioned, that should be fine for backups.

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Answer 5

tbirdvet

Level 6

17,060 points

Oct 17, 2023 6:03 AM in response to SalAlexander

I use the same enclosure with WD NVME drives and no issues however not as a Time machine. I would not use sleep on the newer Macs. They have a tendency to cause issues by ejecting TM drives (and others) upon waking up. Just turn off display or use a screen saver. The card is designed to throttle down the process if temps get too high but perhaps in your case it did not work properly.

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Answer 6

Oct 13, 2023 5:20 AM in response to SalAlexander

At this point I would personally return the WD drive if possible and get a Samsung 980 Pro or possibly an OWC Aura Pro NVMe, especially considering the flakiness at the start of your adventure I would simply not trust either 850x as being reliable.

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Answer 7

Oct 14, 2023 5:34 AM in response to SalAlexander

SalAlexander wrote:

...

I will have spent more money on storage than I spent on the Mac Mini M2 Pro argggggh.... I wish the Mini allowed easier SSD expansion in retrospect.

...

Issues with SSDs and DIY enclosures are not limited to Macs as some combos are problematic on PCs as well.

From a few sources I have seen on the internet, the Acasis enclosures seem like Samsung 980 Pros when used with Macs. There have been other SSDs that have been tested that would work well for one but the same SSD would be problematic for others.

Personally, I think it is possible that USB4/Thunderbolt4, still in its infancy, may still be experiencing growing pains. I see many USB4 offerings from different manufacturers getting less than stellar reviews on most retailer sites, i.e. 20% or more one and two star ratings. Given that more people will post bad experiences than good, it's not a good sign. I was seriously considering the DIY route but my research uncovering the "iffiness" of having just the right combination of SSD and enclosure kind of lead me away from it.

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Answer 8

den.thed

Level 10

90,868 points

Oct 12, 2023 6:19 AM in response to SalAlexander

Time Machine doesn't really require the speediest drives on the market.

Personally I would use Clone-ware like CarbonCopyCloner or SuperDuper for backup on the second DIY 4T MVMe drive and then use a larger SATA SSD or HDD for Time Machine.

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Answer 9

SalAlexander Author

Level 1

12 points

Oct 12, 2023 6:29 PM in response to woodmeister50

I updated the firmware on the WD SSDs, reformatted the Time Machine drive, and the time machine backup failed again at about 77% of about 1.5tb when using a foot long Thunderbolt 4 capable cable. The computer never went to sleep as I kept it awake.

I had a fan blowing on the external enclosure and it was barely warm when it disconnected. So I no longer think it is an overheating issue.

If I leave the drive connected to the Thunderbolt 4 port overnight the Time Machine drive will usually disconnect itself overnight.

I am waiting to hear back from the enclosure manufacturer.

Thanks.

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Answer 10

SalAlexander Author

Level 1

12 points

Oct 13, 2023 5:57 AM in response to woodmeister50

I bought the WD drives from Best Buy in March so am probably stuck with them, but I will try.

I agree with you Woodmeister50: It is very worrisome to continue using a still failing replacement backup drive that is identical to my boot and data drive. I may just buy the Samsung 990 Pro 4tb and try it whether I get a refund or not.

I will have spent more money on storage than I spent on the Mac Mini M2 Pro argggggh.... I wish the Mini allowed easier SSD expansion in retrospect.

I am trying all of these suggestions and once I have stable drives I will update this thread so that other people in my boat can find the best answer - thanks each of you for your help and concern !

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Answer 11

Oct 17, 2023 5:42 AM in response to SalAlexander

Forget the 990 Pro and get the 980 Pro which is much cheaper. You will not gain any performance by getting the 990 over the 980 as your bandwidth will be limited by the Thunderbolt/USB4 bus speeds. Even the 980 Pro access speeds will never be achieved when connected via the Thunderbolt/USB4 bus. Generally, the fastest file transfer speeds you can get on the TB/USB4 bus will be around 2500-2800 megabytes/second. So, spending that extra money on the 990 Pro is, in my opinion, is a waste of money. Plus, Acasis has test proven the 980 Pro!

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Answer 12

SalAlexander Author

Level 1

12 points

Oct 17, 2023 6:37 AM in response to woodmeister50

I just looked at 980 Pro cards - I need 4tb - that's why I went for WD - I'll wait until they test a 4tb Samsung on this enclosure. In the meantime: if I hook the enclosure up through the USB-A it doesn't crash.

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Answer 13

SalAlexander Author

Level 1

12 points

Oct 17, 2023 7:06 AM in response to SalAlexander

Somebody from Samsung Tech Support said "As long as the enclosure supports PCIe M.2 2280, the 990 Pro should be compatible."

WOOHOOOOO I wish I had waited and bought the Samsung SSD. I will try to sell one of the WD SN850X drives, get the Samsung, and let everybody know if it works.

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