Replace a Disk on a Model E Appliance

A model E appliance is equipped with two Solid State Disks (SSDs). When a disk becomes faulty, you can replace it using the mwg-raid tool.

The disks are partitioned and configured for RAID-1.

1. Log on to the appliance where you want to replace a disk from a local system console or remotely using SSH.
   
   When connecting with SSH, consider using a terminal multiplexer to ensure that the replacement procedure does not fail due to an unstable or broken SSH connection.
   
   You can use the tmux multiplexer that Web Gateway has installed.
    
2. Locate the disk that you want to remove.
   
   The two disks on the appliance are named sda and sdb. Run this command to find out which disk is located where
   
   :mwg-raid locate sd<x>
   
   where <x> is either a or b.
   
   The LED on disk sda or sdb starts blinking.
    
3. Run this command to remove the disk from the RAID configuration before you remove it physically.
   In the command, specify sda or sdb depending on which disk you want to remove.
   
   mwg-raid remove sd<x>
   
   This removes the disk from all RAID volumes where it was a member.
   
   The LED on the disk turns to continuous red, as the disk status must be faulty before a disk can be physically removed.
    
4. Remove the old disk from the slot on the appliance hardware platform and insert the new.
5. Run this command to add the new disk to the RAID configuration.
   
   mwg-raid add sd<x>
   
   The new disk is added to the RAID configuration. The content of the disk that was removed is mirrored on the new disk.
   
   While this process is going on, the red LED blinks slowly.
    
6. To check whether the replacement has been performed correctly, run this command:
   
   mwg-raid list
    
7. The command might output the following:

# mwg-raid list
md0      raid1 clean
md0:0    sda1
md0:1    sdb1
md1      raid1 clean
md1:0    sda2
md1:1    sdb2

This output shows that RAID-1 status has been set up again for the disks on the appliance.