Fixing a broken mdadm array – failed drive

Sometimes, even with the best intentions things can go wrong with a RAID array. A drive may fail, or the array may become ‘dirty’ for any number of reasons.

Here, we will go through some simple steps to repair a damaged array.

In our example case, a drive has failed. By running the following command in a terminal, we can get a status update on our array:

    sudo mdadm --detail /dev/md0 # Displays detail about /dev/md0

The output:

failed.png

You can see the state is listed as “clean, degraded” this means a drive is missing from the array. Also note that device 1 has been “removed”.

Before we do anything, we need to unmount our array (in this case, /dev/md0)

    sudo umount /dev/md0 # Unmounts /dev/md0

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Backing up Microsoft Outlook PST files

Sometimes, you may find that you wish to move or backup the PST archive files you have created in Microsoft Outlook. In this walkthrough, we show you how to find these files so they may be copied, moved or backed up.

Open Microsoft Outlook Right-Click on your ‘Personal Folders’ file (note, this may be called Archive or similar) and select Properties

In this walkthrough, I’ve used Outlook 2003, however the process is similar for all versions of Outlook.

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Generating a RAID Five array in Ubuntu with MDADM

Software RAID-5 is a cheap and easy way to create a virtual single drive from many to store your files. Software RAID in Linux, via mdadm, offers lots of advanced features that are only normally available on harware RAID controller cards. A big one is the ability to ‘grow’ the array of disks when you run out of space! Consider also that software RAID can move with you – so if you decide to change motherboards or your RAID controller fails it is won’t mean the end of the world.

This guide details setting up software RAID 5 on Hardy Heron (8.04) Ubuntu using mdadm after you have a running Ubuntu install. It does not cover everything you need to know about RAID and the knowledge in this document is by no means extensive – please check out the further reading link for more information at the end of this article.

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