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Hello I'm trying to figure out how I can create a pretty strange mdadm mirror of my lvm.

I have 4 disks, (sda,b,c,d). Each disk has 2 partitions: 1Gb - physical volume 500mb - Swap

My system lvm volume is currently made of two physical drives:

/dev/sda1 - 1Gb
/dev/sdb1 - 1Gb

Creating a 2Gb volume group for my root partition.

/dev/mapper/sys-root

What I want to do now is mirror my sys-root volume onto the other two disks. I originally thought I would create mirror as:

 mdadm --create /dev/md0 --level=1 --raid-disks=4 missing missing /dev/sdc1 /dev/sdd1

Except I realise that all that would do is mirror the the contents of 1 drive onto the other 3.

What would be the method of mirroring /dev/mapper/sys-root onto my other 2 disks? Unfortunately doing this from scratch isn't an option as I need to use the existing file system.

share|improve this question
    
What exactly do you want for your disk layouts? Do you want two RAID1's with LVM ontop merging them? Or would a RAID10 with the filesystem (with or without LVM) on top be ok? Also, do you need that specific filesystem, or you just want to keep all or your data safe while adding the RAID and don't want to back it up first? – MJD Aug 24 '13 at 15:04

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