CentOS - Apr 2006 - Building software RAID mdmad adding a second disk

Quoting israel.garcia at cimex.com.cu:
> How can I build a RAID 1 of all my particions of sda using mdadm?
1. Boot into rescue mode.

2. Shrink each file system a bit.  Generally you'll use resize2fs 
utility.  MD uses some space at the end of partition for its metadata, 
and you don't want this to overwrite the end of your filesystem.  Most 
HOWTOs on the net list this as one of the last steps (after mirrors are 
created).  However if you do this as last step, in rare cases it may 
lead to data loss.  You probably want to be on the safe side and shrink 
file systems first (this will insure your data is secure).  I'm not 
sure by how much you need to shrink, should be somewhere in 
documentation how many sectors at end of partition MD uses for 
metadata...

3. Create mirror(s) using mdadm.  Create using only one real partition 
and use "missing" instead of second partition (wish Anaconda installer
would allow for something like this).  Then use mdadm to add second 
partition to the mirror.  Something like:

# mdadm --create /dev/md0 --run --level=1 --raid-devices=2 /dev/sda1 missing
# mdadm /dev/md0 -a /dev/sdb1

4. Edit /etc/fstab file.

5. You'll need to rebuild initrd image(s) for installed kernel(s).  
Just mount your filesystems somewhere, chroot into it and run mkinitrd. 
  Mkinitrd should be smart enough to figure it'll need md device 
drivers by looking into fstab file.  Use -v option to mkinitrd to make 
sure it included needed drivers into new initrd image.

6. Configure boot loader (LILO or Grub, whicever you use) to reflect 
changes.  Make sure you install boot loader into MBR of both drives.

-- 
See Ya' later, alligator!
http://www.8-P.ca/

I'am running CentOS 4.3 on an (Intel) with one SATA disk (/dev/sda). 
The output of fdisk -l:

Disk /dev/sda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          19      152586   83  Linux
/dev/sda2              20        2569    20482875   83  Linux
/dev/sda3            2570        2700     1052257+  82  Linux swap
/dev/sda4            2701        9964    58348080    5  Extended
/dev/sda5            2701        9964    58348048+  83  Linux

So, I have an identical second disk (sdb) connected...

My question is:

How can I build a RAID 1 of all my particions of sda using mdadm?

Something like this:

/dev/md0 --> /dev/sda1 and /dev/sdb1
/dev/md1 --> /dev/sda2 and /dev/sdb2
/dev/md2 --> /dev/sda5 and /dev/sdb5

Regards
Israel

Thanks Alexandar for your soon answer, BUT, is there another easier way
to do this?

Regards,
Israel
>>Quoting israel.garcia at cimex.com.cu:
> >>How can I build a RAID 1 of all my particions of sda using mdadm?
>>1. Boot into rescue mode.
>>2. Shrink each file system a bit.  Generally you'll use resize2fs 
>>utility.  MD uses some space at the end of partition for its metadata,
>>and you don't want this to overwrite the end of your filesystem. 
Most
>>HOWTOs on the net list this as one of the last steps (after mirrors
are 
>>created).  However if you do this as last step, in rare cases it may 
>>lead to data loss.  You probably want to be on the safe side and
shrink 
>>file systems first (this will insure your data is secure).  I'm not 
>>sure by how much you need to shrink, should be somewhere in 
>>documentation how many sectors at end of partition MD uses for 
>>metadata...
>>3. Create mirror(s) using mdadm.  Create using only one real partition
>>and use "missing" instead of second partition (wish Anaconda
installer
>>would allow for something like this).  Then use mdadm to add second 
>>partition to the mirror.  Something like:
>># mdadm --create /dev/md0 --run --level=1 --raid-devices=2 /dev/sda1
>>missing
>># mdadm /dev/md0 -a /dev/sdb1
>>4. Edit /etc/fstab file.
>>5. You'll need to rebuild initrd image(s) for installed kernel(s).  
>>Just mount your filesystems somewhere, chroot into it and run
mkinitrd. 
>>  Mkinitrd should be smart enough to figure it'll need md device 
>>drivers by looking into fstab file.  Use -v option to mkinitrd to make
>>sure it included needed drivers into new initrd image.
>>6. Configure boot loader (LILO or Grub, whicever you use) to reflect 
>>changes.  Make sure you install boot loader into MBR of both drives.
>>-- 
>>See Ya' later, alligator!
>>http://www.8-P.ca/