raid-one

[Les Mikesell]

Karl Larsen wrote:

>> The tricky parts are dealing with what happens if you make duplicate 
>> filesystem labels and making the new drive bootable.  But those can be 
>> fixed with a rescue-mode boot.
>>
> Well guys I just set up my first raid-1 system. Here is what it said:
> 
> [root at k5di etc]# cat /proc/mdstat
> Personalities : [raid1]
> md5 : active raid1 sda5[0]
>      5124608 blocks [2/1] [U_]
>     unused devices: <none>
> [root at k5di etc]#
> 
> I did this over lunch and it took several fdisk efforts lots of root 
> terminal things like mkfs and cp -a and such but now on this computer is 
> all of f7 /dev/sdb5 and on the other hard drive I have /home at 
> /dev/sda5 through the raid 1 system. It appears to be working fine and 
> to do the whole thing requires more repeated things and another step to 
> get grub happy :-)


It can be harder than this, though. Consider what happens after you have 
been doing this for a while and are re-using disks that already have 
auto-detect md devices on them and/or filesystem labels that may 
conflict with ones you are using.  Some of the quirkier disk controllers 
can also map a volume into the position where it was configured, even if 
you move it or move to a different machine.  You might pull a disk from 
the 2nd position on one machine, move it to the first position on a 
different machine and add an unconfigured disk in the 2nd position and 
have the 2nd drive come up as /dev/sda.

But, as long as your new drive hasn't been used, an 'fdisk -l' will show 
you which does not have partitions.
-- 
   Les Mikesell
    lesmikesell at gmail.com