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kaizoku

Member

Registered: 2009-01-09

Posts: 62

[Solved] software raid installation

I came across this article http://www.uplinkzero.com/howto/arch_li … tion_guide

I have a few questions to ask.

What is the difference between that setup and just using 1 array.

[root@archlive ~]# mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
[root@archlive ~]# mdadm --create --verbose /dev/md2 --level=1 --raid-devices=2 /dev/sda2 /dev/sdb2
[root@archlive ~]# mdadm --create --verbose /dev/md3 --level=0 --raid-devices=2 /dev/sda3 /dev/sdb3
[root@archlive ~]# mdadm --create --verbose /dev/md4 --level=0 --raid-devices=2 /dev/sda4 /dev/sdb4
[root@archlive ~]# mkfs.ext2 /dev/md1
[root@archlive ~]# mkfs.ext3 /dev/md3
[root@archlive ~]# mkreiserfs /dev/md4
[root@archlive ~]# mkswap /dev/md2
[root@archlive ~]# swapon /dev/md2

compared to

[root@archlive ~]# mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sda /dev/sdb
[root@archlive ~]# cfdisk /dev/md0
[root@archlive ~]# mkfs.ext2 /dev/md0p1
[root@archlive ~]# mkfs.ext3 /dev/md0p3
[root@archlive ~]# mkreiserfs /dev/md0p4
[root@archlive ~]# mkswap /dev/md0p2
[root@archlive ~]# swapon /dev/md0p2

Also it says "/boot must be RAID1", why so?

Last edited by kaizoku (2009-12-25 23:29:18)

_AA_

Member

From: Maidstone, UK

Registered: 2008-07-14

Posts: 19

Website

Re: [Solved] software raid installation

As it's my page I'll reply...

Any linux installation will normally have a minimum of 2 partitions.
/ and SWAP.

In my raid guide I've used 4.
/
/boot
/home
SWAP

But because I want each partition to be part of a RAID array, I've had to create mdX devices.

/boot MUST be RAID 1 for the simple reason that if you lose a disk, you can still boot, assuming of course that / and other parts of the file system required to boot the machines are accessible.

You could probably use RAID 0 (edit) you can't use RAID 0 because GRUB can't read RAID 0 (/edit)

The MBR for obvious reasons should be identical on both drives.

Last edited by _AA_ (2009-12-25 17:58:08)

_AA_

Member

From: Maidstone, UK

Registered: 2008-07-14

Posts: 19

Website

Re: [Solved] software raid installation

http://osmirrors.cerias.purdue.edu/pub/ … E_RAID.TXT
Search for: === Partition hard drives ===

BIOS will not understand /boot partition if it's striped. In fact, even if RAID 0 was built into the initrd image, as it's saved in /boot it still wouldn't work.

Grub installed in the MBR would need to understand RAID0 which as far as I know it doesn't.

kaizoku

Member

Registered: 2009-01-09

Posts: 62

Re: [Solved] software raid installation

I see, thanks for reply and good explaination.