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[NFX] vSRX VNF is set to factory default configuration after power outage

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Article ID: KB34649 KB Last Updated: 22 Apr 2020Version: 3.0
Summary:

An unexpected power outage occurred on NFX250, and the vSRX VNF was created with the factory default configuration. The configuration had to be restored from a backup. All other components were fine.​

Symptoms:

Cache setting is 'none' for data, configuration block device. In case of a power outage, there is the possibility that the config virtual block caches will not be flushed to the disk which may cause config disk corruption.

Example 15.1X49-D78.4:

</disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/junos/images/0/vjunos-config.img'/>
      <target dev='vdc' bus='virtio'/>
      <alias name='virtio-disk2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </disk>
Solution:

The writethrough cache function has been added to Junos OS 18.4 and later images. The recommendation is to upgrade the vSRX to a fixed version.

​Fixed XML:

</disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='writethrough'/>
      <source file='/junos/images/0/vjunos-config.img'/>
      <target dev='vdc' bus='virtio'/>
      <alias name='virtio-disk2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </disk>​


Fixed Releases:  All 18.4 Releases.

The recommended device-cache configuration for vSRX is writethrough. This is for vSRX2 and vSRX3. For other vendor VNF's, it is recommended to clarify with the vendor what the driver-cache mechanism should be for that type of VNF.
 

If adding the following command to a newly created VNF configuration then 'writethrough' cache will appear in the dumpxml output:

set virtual-network-functions vsrx-Name image driver-cache writethrough
 

If you are adding 'writethrough' cache to an already existing configuration, follow the steps below:

  1. From the JDM shell, destroy the VNF with the command:
    root@jdm:~# virsh destroy vsrx
     
  2. From the CLI, remove the configuration for the VNF:
    root@jdm# delete virtual-network-functions vsrx-vnf
    root@jdm# commit
     
  3. Modify the configuration adding the following command:
    set virtual-network-functions vsrx-Name image driver-cache writethrough
     
  4. Then add the rest of the VNF configuration back to create the VNF. Once you commit the configuration change, go to JDM shell and type the following command, and you will see "writethrough" appear in the config as follows:
    root@jdm:~# virsh dumpxml vsrx-vnf
    <SNIP>
         <disk type='file' device='disk'>
          <driver name='qemu' type='qcow2' cache='writethrough'/>
    <SNIP>
Modification History:
2020-04-21: Updated Solution field with fixed version.
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