Creating A Raid 6; Creating Nested Raid 10 Devices With Mdadm; Understanding Nested Raid Devices - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007 Administration Manual

7.1.2 Creating a RAID 6

The procedure in this section creates a RAID 6 device /dev/md0 with four devices: /dev/sda1,
/dev/sdb1, /dev/sdc1, and /dev/sdd1. Make sure to modify the procedure to use your
actual device nodes.
1 Open a terminal console, then log in as the root user or equivalent.
2 Create a RAID 6 device. At the command prompt, enter
3 Create a file system on the RAID 6 device /dev/md0, such as a Reiser file system (reiserfs).
4 Edit the /etc/mdadm.conf file to add entries for the component devices and the RAID
5 Edit the /etc/fstab file to add an entry for the RAID 6 device /dev/md0.
6 Reboot the server.
7 (Optional) Add a hot spare to service the RAID array. For example, at the command prompt
7.2 Creating Nested RAID 10 Devices with
mdadm

7.2.1 Understanding Nested RAID Devices

A nested RAID device consists of a RAID array that uses another RAID array as its basic element,
instead of using physical disks. The goal of this configuration is to improve the performance and
fault tolerance of the RAID.
Linux supports nesting of RAID 1 (mirroring) and RAID 0 (striping) arrays. Generally, this
combination is referred to as RAID 10. To distinguish the order of the nesting, this document uses
the following terminology:
82 SLES 10 Storage Administration Guide
mdadm --create /dev/md0 --run --level=raid6 --chunk=128 --raid-
devices=4 /dev/sdb1 /dev/sdc1 /dev/sdc1 /dev/sdd1
The default chunk size is 64 (KB).
For example, at the command prompt, enter
mkfs.reiserfs /dev/md0
Modify the command if you want to use a different file system.
device /dev/md0.
The RAID 6 device is mounted to /local.
enter:
mdadm /dev/md0 -a /dev/sde1
Section 7.2.1, "Understanding Nested RAID Devices," on page 82
Section 7.2.2, "Creating Nested RAID 10 (1+0) with mdadm," on page 83
Section 7.2.3, "Creating Nested RAID 10 (0+1) with mdadm," on page 84
RAID 1+0: RAID 1 (mirror) arrays are built first, then combined to form a RAID 0 (stripe)
array.
RAID 0+1: RAID 0 (stripe) arrays are built first, then combined to form a RAID 1 (mirror)
array.