Creating A Raid 6; Creating Nested Raid 10 Devices With Mdadm; Understanding Nested Raid Devices - Novell LINUX ENTERPRISE SERVER 10 SP2 - STORAGE ADMINISTRATION GUIDE 05-15-2009 Administration Manual

7.1.2 Creating a RAID 6

The procedure in this section creates a RAID 6 device
,
dev/sdb1
device nodes.
1 Open a terminal console, then log in as the
2 Create a RAID 6 device. At the command prompt, enter
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).
3 Create a file system on the RAID 6 device
For example, at the command prompt, enter
mkfs.reiserfs /dev/md0
Modify the command if you want to use a different file system.
4 Edit the
/dev/md0
5 Edit the
6 Reboot the server.
The RAID 6 device is mounted to
7 (Optional) Add a hot spare to service the RAID array. For example, at the command prompt
enter:
mdadm /dev/md0 -a /dev/sde1
7.2 Creating Nested RAID 10 Devices with
mdadm
Section 7.2.1, "Understanding Nested RAID Devices," on page 98
Section 7.2.2, "Creating Nested RAID 10 (1+0) with mdadm," on page 99
Section 7.2.3, "Creating Nested RAID 10 (0+1) with mdadm," on page 100

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:
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.
98 SLES 10 SP2: Storage Administration Guide
, and
/dev/sdc1 /dev/sdd1
file to add entries for the component devices and the RAID device
/etc/mdadm.conf
.
file to add an entry for the RAID 6 device
/etc/fstab
/dev/md0
. Make sure to modify the procedure to use your actual
user or equivalent.
root
, such as a Reiser file system (reiserfs).
/dev/md0
.
/local
with four devices:
/dev/sda1
.
/dev/md0
,
/