Creating Nested Raid 10 (0+1) With Mdadm - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE FOR EVMS Administration Manual

Table 7-3
Devices
/dev/sdb1
/dev/sdc1
/dev/sdd1
/dev/sde1
1 Open a terminal console, then log in as the root user or equivalent.
2 Create 2 software RAID 1 devices, using two different devices for each RAID 1 device. At the
3 Create the nested RAID 1+0 device. At the command prompt, enter the following command
4 Create a file system on the RAID 1+0 device /dev/md2, such as a Reiser file system
5 Edit the /etc/mdadm.conf file to add entries for the component devices and the RAID
6 Edit the /etc/fstab file to add an entry for the RAID 1+0 device /dev/md2.
7 Reboot the server.
8 (Optional) Add hot spares to service the underlying RAID 1 mirrors.

7.2.3 Creating Nested RAID 10 (0+1) with mdadm

A nested RAID 0+1 is built by creating two to four RAID 0 (striping) devices, then mirroring them
as component devices in a RAID 1.
IMPORTANT: If you need to manage multiple connections to the devices, you must configure
multipath I/O before configuring the RAID devices. For information, see
Multipath I/O for Devices," on page
In this configuration, spare devices cannot be specified for the underlying RAID 0 devices because
RAID 0 cannot tolerate a device loss. If a device fails on one side of the mirror, you must create a
replacement RAID 0 device, than add it into the mirror.
78 SLES 10 Storage Administration Guide for EVMS
Scenario for Creating a RAID 10 (1+0) by Nesting
command prompt, enter these two commands:
mdadm --create /dev/md0 --run --level=1 --raid-devices=2 /dev/sdb1
/dev/sdc1
mdadm --create /dev/md1 --run --level=1 --raid-devices=2 /dev/sdd1
/dev/sde1
using the software RAID 1 devices you created in
mdadm --create /dev/md2 --run --level=0 --chunk=64 --raid-devices=2
/dev/md0 /dev/md1
The default chunk size is 64 (KB).
(reiserfs). For example, at the command prompt, enter
mkfs.reiserfs /dev/md2
Modify the command if you want to use a different file system.
device /dev/md2.
The RAID 1+0 device is mounted to /local.
For information, see Section 6.4, "Adding or Removing a Spare Disk," on page
RAID 1 (mirror)
/dev/md0
/dev/md1
Step
41.
RAID 1+0 (striped mirrors)
/dev/md2
2:
64.
Chapter 5, "Managing