Applies to:
Operating System(s) - Oracle Linux 6.x, RHEL 6.x
Server Platform(s) - PowerEdge R720, R820
Author:
Naveen Iyengar
Problem:
How to configure software RAID on Dell Express Flash PCIe SSDs
Solution:
1. Identify the Express Flash block devices – Dell’s Micron Express Flash drives show up as the following block devices in EL6.x OS
$> cat /proc/partitions
Major minor #blocks name
251 256 341873784 rssda
251 512 341873784 rssdb
2. Create a Partition – Use the fdisk linux utility as follows to create an 'fd' type partition on the Flash drives
$> fdisk –u /dev/rssda
Command (m for help):
n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4):
1
First sector (56-683747567, default 56:
128
Last sector, +sectors or +size…, default 683747567:
<hit Enter>
Command (m for help):
t
Selected partition 1
Hex code (type L to list codes):
fd
Changed system type of partition 1 to fd (Linux raid autodetect)
Command (m for help):
wq
The partition table has been altered!
$>
3. Repeat step 2 for all the other PCIe SSD block devices to be included in the software RAID
4. Create software RAID – Use the Linux utility tool called mdadm as follows to create the software RAID array on the Express Flash drives. The following example create a RAID1 using two Flash drives /dev/rssda1 and /dev/rssdb1.
$> mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/rssd[ab]1
5. Viewing the details of the array: View the status of the multi disk array md0.
$> mdadm --detail /dev/md0
6. Make the array persistent across reboots: To add md0 to the configuration file so that it is recognized next time on boot, do the following:
$> mdadm -Es | grep md0
Check if the above command displays the details of the md0 array created. If not, try
$> mdadm -Es | grep "md/0"
Depending on which of the above two command works, run the appropriate command below to add info to the mdadm.conf file
$> mdadm -Es | grep md0 >> /etc/mdadm.conf
Or
$> mdadm -Es | grep "md/0" >> /etc/mdadm.conf
7. Check for resync complete: Run the --detail option to make sure that the two SSDs in the array are not in the Resync Status, or wait until it finishes resyncing before you run a test against them.
$> mdadm --detail /dev/md0
A. Deleting the array:
$> mdadm --stop /dev/md0
- Delete the superblock from all drives in the array
$> mdadm --zero-superblock /dev/sd[abc]1
- Edit /etc/mdadm.conf to delete any rows related to the deleted array(s)