Description

You may observe that whenever the primary disk (Disk1) fails or goes missing on the Next-Generation Routing Engine (NG-RE), the Routing Engine (RE) boots from the alternate disk (Disk2). This article explains how to troubleshoot this problem.

Symptoms

You will see the following alarm on the chassis:

> show chassis alarms
5 alarms currently active
Alarm time              Class Description
2023-07-17 14:48:16 IST Minor VMHost 1 Boot from alternate disk
2023-07-17 14:48:16 IST Minor VMHost RE 1 Disk 1 Missing

From the below output, you can see the current boot disk as Secondary:

> show vmhost version
Current root details,          Device sdb, Label: jrootp_S, Partition: sdb3
Current boot disk: Secondary
Current root set: p
UEFI   Version: REH_P_MTR1_00.30.07
Secondary Disk, Snapshot Time: Fri Jul 14 10:29:09 IST 2023
Version: set p
VMHost Version: 5.2279
VMHost Root: vmhost-x86_64-20.2R3-S1-20210430_0731_builder
VMHost Core: vmhost-core-x86-64-20.2R3-S1.3
kernel: 4.8.28-rt10-WR9.0.0.24_ovp
Junos Disk: junos-install-mx-x86-64-20.2R3-S1.3
Version: set b
VMHost Version: 5.2279
VMHost Root: vmhost-x86_64-20.2R3-S1-20210430_0731_builder
VMHost Core: vmhost-core-x86-64-20.2R3-S1.3
kernel: 4.8.28-rt10-WR9.0.0.24_ovp
Junos Disk: junos-install-mx-x86-64-20.2R3-S1.3

Solution

To work around this problem, perform the following steps in a Maintenance Window:

  1. Run the command ">request vmhost snapshot recovery partition".
> request vmhost snapshot recovery partition
warning: All existing data on the target media will be lost
Proceed ? [yes,no] (no) yes

Creating snapshot on target disk from current boot disk ...
Primary disk is recovered now. Please issue "request vmhost reboot" to boot from the primary disk.
Software snapshot done

  1. Reboot the RE by using the command "request vmhost reboot" (after the reboot alarm gets cleared).

  2. Check manually whether the disk is missing. If yes, then insert a healthy disk.

  3. Check for a faulty disk and insert a working disk.

  4. Try USB recover, because if the issue is related any file system error/corruption. Then USB recover will format the desk and can fixed it the issue not related to hardware. 
  5. Replace the Routing Engine if the above recovery does not help by contacting Support.

Modification History

2023-07-26: Added logs in the solution section; made formatting changes