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Old 01-06-2009, 11:18 AM   #1
ryanvoon
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Registered: May 2008
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Implement software RAID at running live Linux sever


Dear members,

May I know how to implement software RAID at running live Linux sever.

I saw other site on implementing Software RAID at installation stage, but how about a running Linux ( RHEL v5).

I tried to bring down to level 1 , and do mdadm --create /dev/md0 .

But it failed. I am not able to create md0, 1 , 2 ,3 etc

The type of sda 1,2,3,4 sdb 1,2,3,4 was already fd when i did fdisk ( Option : T )

Thanks alot.
Ryan
 
Old 01-07-2009, 03:58 AM   #2
eco
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Registered: May 2006
Location: BE
Distribution: Debian/Gentoo
Posts: 412

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Hi,

You need to setup the environment for RAID before you start building the RAID...

Here are extracts of a few notes I wrote:

// load module(s)
# modprobe raid1
# lsmod | grep raid
raid1 16000 0
md 44744 1 raid1


// partition the 'second' disk to be the same as the 'first' (original). You can do that automatically with sfdisk or manually with fdisk.

// install mdadm
# apt-get install mdadm


// I had 9 partitions so I did:
# mkdir /dev/md
# for i in 1 2 3 5 6 7 8 9; do mknod /dev/md/$i b 9 $i; ln -s /dev/md/$i /dev/md$i; done


// Now you need to create a degraded RAID. BACKUP YOUR DATA AND CHECK IT BEFORE DOING THIS
# for i in 1 2 3 5 6 7 8 9; do mdadm --create /dev/md$i --level=1 --raid-devices=2 missing /dev/sdb$i; done
mdadm: array /dev/md1 started.
mdadm: array /dev/md2 started.
mdadm: array /dev/md3 started.
mdadm: array /dev/md5 started.
mdadm: array /dev/md6 started.
mdadm: array /dev/md7 started.
mdadm: array /dev/md8 started.
mdadm: array /dev/md9 started.


// check the status of the RAID creation
# watch cat /proc/mdstat


// for more detail
# mdadm --detail /dev/md1
/dev/md1:
Version : 00.90.01
Creation Time : Wed Jan 24 10:51:39 2007
Raid Level : raid1
Array Size : 104320 (101.88 MiB 106.82 MB)
Device Size : 104320 (101.88 MiB 106.82 MB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Wed Jan 24 10:51:39 2007
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

UUID : 3165639b:c92abf3c:72f0f2b7:767fc1fd
Events : 0.1

Number Major Minor RaidDevice State
0 0 0 - removed
1 8 17 1 active sync /dev/.static/dev/sdb1


//Generate configuration file
mdadm --detail --scan >> /etc/mdadm.conf


//Now change your fstab to point to /dev/mdx rather than sdx, grub, ...
//When all of this is done, boot. If it boots, rebuild the RAID (look on how to do this in the manual of mdadm

# mdadm /dev/md0 -a /dev/<missingdisk>

Best of luck
 
Old 01-07-2009, 10:31 AM   #3
ryanvoon
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Registered: May 2008
Posts: 2

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THanks alot for the info

HI,

THanks for the info. I will try out in dev servers.

Happy New Year
 
  


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