[CentOS] Mirroring Hard Drive

Robert kerplop at sbcglobal.net
Tue Aug 12 16:27:08 UTC 2008

Robert wrote:
> Paul R. Ganci wrote:
>> Matt wrote:
>>>> why not just put it in the machine and make it a raid1
>>>> mirror
>>>> then, if the first one dies, you just use the second one :D
>>> How do you do that?
>> Detailed step by step instructions easily modified for CentOS:
>> http://www.howtoforge.com/software-raid1-grub-boot-debian-etch
>> I haven't tried this myself ... yet but plan on it in the next few 
>> weeks.
> I haven't tried it either...yet... but there is also a version of the 
> HOWTO for Fedora 8, which might require less interpolation. 
> http://www.howtoforge.com/software-raid1-grub-boot-fedora-8
> Thanks for the URL
I should have had the common decency to report that I *did* try this 
howto and *was* successful. There were a couple things that caused some 

1. I read somewhere that it's safest to resize the filesystems on the 
existing drive before doing anything else, to allow for a 4K superblock 
beginning on a 64k boundary at the end of the partition. I did that. 
(Straightforward instructions at 

2. In part 2, page 7, there is a step "Next replace LABEL=/boot with 
/dev/md0 and LABEL=/ with /dev/md2 in /etc/mtab" that I kinda 
questioned.  It was my understanding that /etc/mtab is maintained by the 
mount command. (From man mount: "The programs mount and umount maintain 
a list of currently mounted file systems in  the  file /etc/mtab".)  
This makes the command on page 9, "cp -dpRx / /mnt/md2" *appear* to be 
copying md2 to itself. Confusion aside, the command has the desired result.

Aside from those 2 points, it went very smoothly.

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