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I have an ubuntu 12.04 setup with two HDD that is setup in a software raid 1. Now I need to add two additional SSD drives for separate storage of some database files. They need to be setup in their own separate raid 1 array. Unfortunately I have no idea where and how to start? So from the beginning after having plugged the two drives in, and booted the server - then what?

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up vote 5 down vote accepted

Okay i got it:

1) First list all drives: sudo lshw -c storage -c disk and note down the drives that needs to be put into a new raid array (in my case /dev/sda and /dev/sdb)

1.1) If you need to find out what drives are already in a raid this can be done with sudo cat /etc/mdadm/mdadm.conf details about which drives they cover can be inspected with sudo mdadm --query --detail /dev/md0 where /dev/md0 is the array you want to inspect.

2) Now use fdisk to format the drives and create partitions for each drive: sudo fdisk /dev/sda this is done for each drive (and they should of cause be setup equally)

  • If the disk is not "clean" then press d and follow instructions to delete the current partitions (note all data will be lost on that disk!)
  • Then press n to create a new partition.
  • Press p for primary and 1 for one partition, and use the defaults (pressing return).
  • Press t for type and set the partition type to fd (linux raid autodetect).
  • press w for writing your changes and exit.

3) Create the RAID array: sudo mdadm --create /dev/md3 --chunk=128 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1

4) Format the array: sudo mkfs -t ext4 /dev/md3

5) Lookup the infor for the new array using method in step 1.1 and edit sudo nano /etc/mdadm/mdadm.conf accordingly with the following line for your new array ARRAY /dev/md/3 metadata=1.2 UUID=f368e29e:b79c72bd:631ce90f:e3370f90 name=master-db:3

6) Create a directory (mount dir) for the new drive sudo mkdir /new_device

7) Mount to fstab by editing sudo nano /etc/fstab with /dev/md3 /new_device auto defaults 0 0

8) Run sudo mount -a

Check that everything runs with: sudo cat /proc/mdstat

Some helpfull links: Which hard disk drive is which?

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