Hoping for support on this seemingly niche issue. I don't see anyone else discussing this specific problem.

I updated form 7.2.2 to 7.3 today, and immediately noticed an explosion of BTRFS 'corruption errors' being generated on my cache pool when my Windows 11 VM was running. After running Memtest (clean) and a scrub of my cache pool, I pulled everything off my cache and rebuilt it. During that time, I tried running my VM after moving the vDisk to my other SSD pool, and saw the same behavior:


I just checked my libvert logs for the VM, and I have multiple errors there as well:


I'm assuming something has changed with 7.3 that is causing my VM to generate these errors? Below is my XML, any help would be greatly appreciated!

<?xml version='1.0' encoding='UTF-8'?>
<domain type='kvm' id='1'>
  <name>Win11_LTSC-new</name>
  <uuid>6621b335-dc0a-455a-fd7c-5e7666d0e68c</uuid>
  <metadata>
    <vmtemplate xmlns="unraid" name="Windows 11" iconold="windows11.png" icon="windows11.png" os="windowstpm" webui="" storage="default"/>
  </metadata>
  <memory unit='KiB'>38797312</memory>
  <currentMemory unit='KiB'>38797312</currentMemory>
  <memoryBacking>
    <nosharepages/>
  </memoryBacking>
  <vcpu placement='static'>16</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='2'/>
    <vcpupin vcpu='1' cpuset='14'/>
    <vcpupin vcpu='2' cpuset='3'/>
    <vcpupin vcpu='3' cpuset='15'/>
    <vcpupin vcpu='4' cpuset='4'/>
    <vcpupin vcpu='5' cpuset='16'/>
    <vcpupin vcpu='6' cpuset='5'/>
    <vcpupin vcpu='7' cpuset='17'/>
    <vcpupin vcpu='8' cpuset='8'/>
    <vcpupin vcpu='9' cpuset='20'/>
    <vcpupin vcpu='10' cpuset='9'/>
    <vcpupin vcpu='11' cpuset='21'/>
    <vcpupin vcpu='12' cpuset='10'/>
    <vcpupin vcpu='13' cpuset='22'/>
    <vcpupin vcpu='14' cpuset='11'/>
    <vcpupin vcpu='15' cpuset='23'/>
  </cputune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-q35-10.2'>hvm</type>
    <loader readonly='yes' type='pflash' format='raw'>/usr/share/qemu/ovmf-x64/OVMF_CODE-pure-efi-tpm.fd</loader>
    <nvram format='raw'>/etc/libvirt/qemu/nvram/6621b335-dc0a-455a-fd7c-5e7666d0e68c_VARS-pure-efi-tpm.fd</nvram>
    <smbios mode='host'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv mode='custom'>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vpindex state='on'/>
      <runtime state='on'/>
      <synic state='on'/>
      <stimer state='on'/>
      <reset state='on'/>
      <vendor_id state='on' value='A1B2C3D4E5F6'/>
      <frequencies state='on'/>
      <reenlightenment state='on'/>
      <tlbflush state='on'/>
      <ipi state='on'/>
    </hyperv>
    <kvm>
      <hidden state='on'/>
    </kvm>
    <vmport state='off'/>
  </features>
  <cpu mode='host-passthrough' check='none' migratable='off'>
    <topology sockets='1' dies='1' clusters='1' cores='8' threads='2'/>
    <cache mode='passthrough'/>
    <feature policy='require' name='topoext'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='hpet' present='no'/>
    <timer name='hypervclock' present='yes'/>
    <timer name='tsc' present='yes' mode='native'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/local/sbin/qemu</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none' discard='ignore'/>
      <source file='/mnt/user/domains/Windows/Win11_LTSC/vdisk1.img' index='2'/>
      <backingStore/>
      <target dev='hdc' bus='virtio'/>
      <serial>vdisk1</serial>
      <boot order='1'/>
      <alias name='virtio-disk2'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/mnt/user/isos/virtio-win-0.1.285-1.iso' index='1'/>
      <backingStore/>
      <target dev='hdb' bus='sata'/>
      <readonly/>
      <alias name='sata0-0-1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <controller type='usb' index='0' model='qemu-xhci' ports='15'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'>
      <alias name='pcie.0'/>
    </controller>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x8'/>
      <alias name='pci.1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x9'/>
      <alias name='pci.2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0xa'/>
      <alias name='pci.3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0xb'/>
      <alias name='pci.4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x3'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0xc'/>
      <alias name='pci.5'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x4'/>
    </controller>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0xd'/>
      <alias name='pci.6'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x5'/>
    </controller>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0xe'/>
      <alias name='pci.7'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x6'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    </controller>
    <controller type='sata' index='0'>
      <alias name='ide'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:a5:04:67'/>
      <source bridge='br0'/>
      <target dev='vnet0'/>
      <model type='virtio-net'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      </target>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <channel type='unix'>
      <source mode='bind' path='/run/libvirt/qemu/channel/1-Win11_LTSC-new/org.qemu.guest_agent.0'/>
      <target type='virtio' name='org.qemu.guest_agent.0' state='connected'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <channel type='qemu-vdagent'>
      <source>
        <clipboard copypaste='yes'/>
        <mouse mode='client'/>
      </source>
      <target type='virtio' name='com.redhat.spice.0' state='disconnected'/>
      <alias name='channel1'/>
      <address type='virtio-serial' controller='0' bus='0' port='2'/>
    </channel>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'>
      <alias name='input1'/>
    </input>
    <input type='keyboard' bus='ps2'>
      <alias name='input2'/>
    </input>
    <tpm model='tpm-tis'>
      <backend type='emulator' version='2.0' persistent_state='yes'/>
      <alias name='tpm0'/>
    </tpm>
    <graphics type='vnc' port='5900' autoport='yes' websocket='5700' listen='0.0.0.0' sharePolicy='ignore'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <audio id='1' type='none'/>
    <video>
      <model type='qxl' ram='131072' vram='262144' vram64='262144' vgamem='65536' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1e' function='0x0'/>
    </video>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev0'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0' multifunction='on'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x01' slot='0x00' function='0x1'/>
      </source>
      <alias name='hostdev1'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x1'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x0a' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev2'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x0f' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev3'/>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </hostdev>
    <watchdog model='itco' action='reset'>
      <alias name='watchdog0'/>
    </watchdog>
    <memballoon model='none'/>
  </devices>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+0:+100</label>
    <imagelabel>+0:+100</imagelabel>
  </seclabel>
</domain>

Attach Diagnostics ZIP to your NEXT post in this thread.

Sorry, this is my first post to the forum. I appreciate your patience. Attached the diags below.

tower-diagnostics-20260527-0030.zip

Can you retest without passing through any PCI devices to the VM? Also, do you have ACS override enabled?

Re-tested with no PCI devices passed through, just VNC for remote control. Still generated corruption errors in pool device status and same errors in the VM libvert logs.

I suppose it'd be worthwhile to test if this occurs on a fresh VM as well. I can set one up later this evening and see what happens.

That's bizarre, but yeah, if you can test a new VM with a new vdisk.

Remoted in from work, setup fresh W11 LTSC vm, tested with and without PCI devices passed through, and no errors generated. I'm assuming something has happened to corrupt my original vdisk for my primary VM, so I'll go ahead and transfer that OS image to a new vdisk and test that out. I've seen some others posting about misc behavior of VMs after 7.3 update. Is it possible something with 7.3 borked some VMs?

In regards to transferring OS to a new vdisk, what is best practice? Is it as simple as creating and attaching a vdisk2 to existing VM, using Macrium (or other mirroring software) to mirror OS to vdisk2, then replacing vdisk1 with vdisk2 as primary for VM?

Edit: Additionally, is there a good resource for optimizing KVM XMLs? I understand Unraid's default XML configs are designed more for hardware compatibility than gaming performance. I've read some of the Arch WiKi and that's helped me a bit, but I'm wondering if there's any specific resources y'all recommend?

Edited May 27May 27 by joelong

I am experiencing the same issue but not from a VM just from normal use, extreme btrfs error messages with zero smart issues to back it up.

13 hours ago, squanchy2112 said:

I am experiencing the same issue but not from a VM just from normal use, extreme btrfs error messages with zero smart issues to back it up.

Start your own thread with your diagnostics.

I had the same issue in the past. BTRFS CoW and Win VMs do not play well together. You can search the web and find several examples of similar errors (with nice technical explanations why that happens).

Just disable CoW for the whole share you use for VM files, or for the single files. For instance, in my case, the Linux VMs were not creating any issue, only the Win one.
Unfortunately I cannot tell you the commands I used because I have lost them.

Once I have disabled CoW for the Win VM, all the errors disappeared.