Moving VM to external SSD causes disk errors

[ccalabro]

Hi all,

I can create a win/linux/osx vm on my local drive and works no problem.  Take that vm and move it to an external SSD and only the osx vm will work without issue.  Both the Windows or Linux vm's crash, wont load, or have disk errors.

The SSD is fast and stable.  It happens immediately after the move which is curious.  Even more curious is that any macOS vm's I create work fine regardless.

Can anyone please give me a tip in what i am missing. I dont believe its a hardware/file corruption issue.

Any assistance appreciated.

(Sonoma b3 if that makes any difference)

[Technogeezer]

Please define "crash, won't load or have disk errors". Some exact error messages would be helpful.

What Mac platform are you using?

Is the SSD a USB device, or a Thunderbolt device?

How did you move those VMs to the external SSD? Did you move them with the Finder or some other mechanism?

Do you still have the original VMs on your local drive? Or have a backup of those VMs on another drive that you know are OK (not Time Machine!). If you do, repeating the move (or restoring from your backup copy) might be of interest, but you should also verify that the files copied correctly by comparing the hashes of all the files in the VM's bundle.

You can't rule out a hardware issue, file corruption, or an outright bug in Apple's beta. Does this work properly with macOS Ventura on the same hardware?

I hope this is not a Mac that you are depending on for anything, that you have a backup copy of your VMs, and are prepared to revert back to Ventura if necessary.

 

[ccalabro]

Thanks for the reply. I will get the proper errors, I can only see them in the linux vm’s windows just goes to system repair screeen the fails to boot.

i have the original vm’s on the Mac system drive they work fine. I am just testing them so nothing is critical. 
external drive is usb3.2 ssd in exfat format.

ill collect some more info on the errors.

[ColoradoMarmot]

Let me add one more question - what format is the external drive?  If it's not APFS, reformat it that way and then try again.

 

[ccalabro]

SSD is exfat

[Technogeezer]

Running a VM on ExFAT is a big red flag.

Fusion expects a POSIX compliant file system, and ExFAT formatted disks do not support full POSIX operations. It's very likely that's your problem. ExFAT are good for transfer but not for operation of a VM. And the macOS implementation is not as robust as HFS+ or APFS.

Try that SSD formatted as HFS+ or APFS and see if the symptoms change.

 

[ccalabro]

exFat was the issue.

made SSD APFS partition and the vm's work flawlessly from there.

Thanks for the assistance everyone, greatly appreciated.

[ColoradoMarmot]

Glad it worked out!

[VMware Community Member]

Hi - Just to say something must have changed somewhere, because I ran my dev environment from an exFat formatted SSD for years, then suddenly started having this problem with any exFat formatted drive around the same time as you raised this issue.

[Technogeezer]

I've heard of issues with storing VMs on ExFAT for a while now, but there is one change in Sonoma that might make things worse:

According to the Sonoma release notes:

• The implementations of the exfat and msdos file systems on macOS have changed; these file systems are now provided by services running in user-space instead of by kernel extensions. If the application has explicit checks or support for either the exfat or msdos file systems, validate the applications with those file systems and report any issues. (110421802)

It's a possibility that this change could introduce additional problems for Sonoma and later. In which case that would be an Apple bug if behavior differs from Ventura and earlier. 

 

[VMware Community Member]

Yep - that sounds like a likely culprit!

 

Thanks

[wila]

Hi,

If you've been running from exFAT for years.... then you've been lucky for years...

The format is notorious for silent file corruption. When people complain about my backup software returning warnings on the file hash when restoring a backup.. the first thing I will ask if they are storing the backups on exFAT. Nine out of ten times that is the issue.

This sometimes even already shows up during the backup process as that also runs some checks, although not the full file hash.

This is not unique to macOS either. The same issue with exFAT also happens on the Windows platform.
Don't use exFAT for anything you don't mind a little bit of bitrot on.

Just my 2 cents,

--
Wil

[lensv]

I came across this problem a while ago and I thought that I solved it by reformatting the external drive to Mac OS Extended, but now my VM still crashes from time to time. I noticed that the hard disk is set to NVMe. Would SATA be a better choice for a USB drive?

[Technogeezer]

---

 wrote:

I came across this problem a while ago and I thought that I solved it by reformatting the external drive to Mac OS Extended, but now my VM still crashes from time to time. I noticed that the hard disk is set to NVMe. Would SATA be a better choice for a USB drive?

---

I don’t think so. There’s nothing I know of that ties the virtual disk type (SATA, IDE, SCSI, etc) to the how the disk the VM resides on is connected to the Mac (USB, Thunderbolt, SATA).

Is the VM crashing or Fusion? I have heard of some operating systems having problems with VMware’s NVMe virtual disk controller (with Fusion/Workstation on Intel). Perhaps changing the controller type might help (but that’s easier said than done for an existing VM - best done for a new VM).  On ARM, though, I haven’t seen those issues with NVMe virtual disk types. 

[ColoradoMarmot]

If it's an SSD, APFS is by far the best format for it.

It's also possible that the external drive is starting to fail - have you run health check?

[lensv]

This specific drive is a USB-stick, which has worked before. APFS was not an option on this device though (for some reason?).

Do you have suggestions for a competent health check software?

 

 

 

[Technogeezer]

I have seen complaints about some USB devices having issues with the latest Sonoma 14.4 update. Wondering if that could be part of the problem?

I haven't run VMs from USB sticks because for the most part they are noticeably slower than USB SSDs. But I haven't encountered one that couldn't be reformatted for APFS. A possibility though is that the USB stick is using Master Boot Record (MBR) partitioning.  I don't think APFS can be used on an MBR partitioned disk.  You' should be able to go into Disk Utility and erase and reformat the entire disk. Specify the partitioning type as GPT - that should allow APFS.

[ColoradoMarmot]

USB sticks are notorious for cheap storage, especially non-branded ones.  If repartitioning as GPT and formatting as APFS doesn’t work, I’d consider the stick suspect and look for a different storage solution.

[wila]

Hi,

USB sticks are OK to store a VM on if you want to move it from A to B.

They are much less suitable for running a VM from. They just haven't been designed for high IO write streams. While it might work for a little while.. perhaps even perform OK-ish (if you're lucky).. they will fail rapidly. Much quicker than you would expect.
If you do this in production.. be sure to have a good backup at all times.

An external USB disk (SSD/NVMe or even plain old spinning rust) will outlive your USB stick by a long time.

Please note that ANY external disk for running VM's from is more likely to cause VM disk corruption if only because of the increased risk of disconnecting the disk with the VM running. I'm talking from experience here as it was for some time my solution for running more VM's while on the road.

--
Wil