Alright so I got the basically the same situation as described here.

The differences are:

  • ESXi 6.7.0 fully patched
  • local SSDs and HDDs

The VM is running a common Nextcloud stack (MySQL, Apache2, PHP).

This issue came up just after I upgraded my ESXi to the current patch level (January or February patch I think. There were no other storage related changes on the systems in question. Only thing that comes to my mind is that the VM experiences high disk load, as sometimes both the ghettoVCB and an ssh-based backup overlap.

I can see that the kernel issues messages that point to storage access timeouts. I also just found a log message on the ESXi that reads:
Lost access to volume UUID (name) due to connectivity issues. Recovery attempt is in progress and outcome will be reported shortly.

But there is nothing further reported.

Only solution to get both the VM and ESXi responsible again this is a hard reset of the ESXi host.

I will update this question as my research continues. If anyone has any idea I would highly appreciate your help!


Assuming there is no there are no connectivity issues between the ESXi host and the storage device and you already checked if there are no path inconsistencies to the LUN (if the case), it appears you have a driver compatibility problem caused by ESXi patching.

You could try to disable the vmw_ahci driver:

esxcli system module set --enabled=false --module=vmw_ahci

If that does not work, you should revert to the previous patch of ESXi or try to restore the initial drivers (which may be quite difficult).

Also, checking the vmkernel.log, vobd.log and vmksummary.log may reveal details about the exact cause.


This one was stupidly simple: One hard drive failed which was accessed by this very VM as a data disk. It was physically broken but neither ESXi nor the management board saw that.

TL;DR: A HDD failed but that was not detected. This issue was not software related.

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