From recent kernel and/or vbox versions forward, I've started to experience data loss and/or filesystem corruption on a regular enough basis that I've enabled fsck on every reboot. Mac OSX hosted VM.

It's not clear to me what the source of the problem is, but it may not be ext4 itself vs some element of the block device drivers and/or related hypervisor facilities. The logs have the following information:

Message from syslogd@ubuntu at May 21 15:56:49 ... kernel:[1958392.548682] EXT4-fs (dm-0): failed to convert unwritten extents to written extents -- potential data loss! (inode 259291, error -30)
Message from syslogd@ubuntu at May 21 15:56:50 ... kernel:[1958392.830326] EXT4-fs (dm-0): failed to convert unwritten extents to written extents -- potential data loss! (inode 262111, error -30)

There is some multi-factor problem going on here, and frankly, I don't even know where to start in order to determine the cause! This is a linux virtual machine hosted by virtualbox on mac os x.

One possibility is that this occurs when the os x system is under relatively high load. Under 5x kernel versions on this VB host I have also seen some occasional CPU X stuck for 22s messages. However these messages have not been correlated with the ext4 errors.

The problem is not completely deterministic; there's no specific set of circumstances that always produces this result.

What further steps for fault finding is suggested?

EDIT: Additions of version information and other specifics (which I could have sworn were part of the originally linked-to discussion, woops!). Note, this probably started at some point in the 5.x kernel series and 6.1.x VirtualBox series and late Mac OS 10.x and Big Sur 11.6.x -- i.e., I'm quite sure the proximal cause was upgrades to Linux Kernel and Virtual Box, not changes to Mac OS.

Linux ubuntu 5.13.0-35-generic #40-Ubuntu SMP Mon Mar 7 08:03:10 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

VirtualBox Version 6.1.34 r150636 (Qt5.6.3)

Host OS: Mac OS Big Sur 11.6.6

VBoxGuestAdditions-6.1.34

A possibly related issue was what seemed to be extremely slow block device/hard drive performance for a while, which seemed to respond to updating the guest additions. This was fairly extensively discussed in response to a question I posted on the VirtualBox Linux Guest discussion group here:

Performance was in the 500kB/sec and is now in the 20MB/sec. Both seem very slow.

Please excuse the external link but it just doesn't make sense to copy/paste the entire thread.

If anyone has comparative read MB/s numbers for a similar setup that would be helpful.

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