[CentOS] software raid - better management advice needed

Thu Jun 10 00:36:33 UTC 2010
Robert Heller <heller at deepsoft.com>

At Wed, 9 Jun 2010 16:50:53 -0700 CentOS mailing list <centos at centos.org> wrote:

> 
> Hi,
> 
> I've used mdadm for years now to manage software raids.
> 
> The task of using fdisk to first create partitions on a spare drive  
> sitting on a shelf (raid 0 were my 1st of 2 drives failed) is kind of  
> bugging me now.
> 
> After using fdisk to create the same partition layout on the new drive  
> as is on the existing drive and then using mdadm to finish every thing  
> up is a little tedious.
> 
> Any one have an idea how to have a sort of hot plug were I just swap  
> out the drive and it rebuilds?

sfdisk is your friend (from man sfdisk):

       -d     Dump the partitions of a device in a format useful as input  to
              sfdisk. For example,
                  % sfdisk -d /dev/hda > hda.out
                  % sfdisk /dev/hda < hda.out
              will correct the bad last extended partition that the OS/2 fdisk
              creates.

So:

1) plug in replacement disk.
2) partition it:

# sfdisk -d /dev/sdX | sfdisk /dev/sdY

Where /dev/sdX is an existing disk and /dev/sdY is the replacement disk

3) add the partition(s) to the array(s):

# mdadm /dev/mdI ... -a /dev/sdYI
# mdadm /dev/mdJ ... -a /dev/sdYJ
# mdadm /dev/mdK ... -a /dev/sdYK
# mdadm /dev/mdL ... -a /dev/sdYL

No reason not to put all of the above in a script...

> 
> 
> - aurf
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>                                                

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