===========================================
LVM vs S/W mirroring comparison environment
===========================================

Environment
-----------

    *   Test environment consists of a Centos 6.3 Kernel Virtual Machine (guest).
    *   Two virtual disks, hdb and hdc, 10 gigs each.

Set up
------

    *   guest shut down:

    ::

        # virsh list --all
         Id    Name                           State
         ----------------------------------------------------
         9     guest1                         running
         10    python                         running
         -     guest                          shut off

    *   Verify no pre-existing disks:

    ::

        # virsh vol-list default
        Name                 Path                                    
        -----------------------------------------
        guest.img            /var/lib/libvirt/images/guest.img       
        guest1.img           /var/lib/libvirt/images/guest1.img      
        python.img           /var/lib/libvirt/images/python.img     

    *   Create volumes, add them to guest, and restart guest

    ::

        for x in 1 2
        do
        echo virsh vol-create-as default guest-${x}.img 10g
        virsh vol-create-as default guest-${x}.img 10g
        done
        virsh vol-create-as default guest-1.img 10g
        Vol guest-1.img created
        .
        virsh vol-create-as default guest-2.img 10g
        Vol guest-2.img created
        .
        # virsh vol-list default | grep guest
        guest-1.img          /var/lib/libvirt/images/guest-1.img     
        guest-2.img          /var/lib/libvirt/images/guest-2.img     
        guest.img            /var/lib/libvirt/images/guest.img       
        guest1.img           /var/lib/libvirt/images/guest1.img
        .
        # virsh attach-disk guest /var/lib/libvirt/images/guest-1.img hdb --persistent
        Disk attached successfully
        .
        # virsh attach-disk guest /var/lib/libvirt/images/guest-2.img hdc --persistent
        Disk attached successfully
        .
        # virsh domblklist guest
        Target     Source
        ------------------------------------------------
        hda        /var/lib/libvirt/images/guest.img
        hdb        /var/lib/libvirt/images/guest-1.img
        hdc        /var/lib/libvirt/images/guest-2.img
        .
        # virsh start guest
        Domain guest started

    *   Verify new disks on guest

    ::

        # h  
        guest
        # grep sd /proc/partitions | sort -k 4
           8        0   20971520 sda
           8        1     512000 sda1
           8        2   20458496 sda2
           8       16   10485760 sdb
           8       32   10485760 sdc


Script
------

    Straight forward scrpt to ensure repeatability:

    ::


        #!/bin/ksh
        
        # shut down guest if required:
        
        echo 'Checking if guest is running'
        virsh list --all | grep -i guest | grep -v guest1 | \
            grep -qi running && virsh destroy guest
        
        # remove disks from guest:
        
        echo 'Removing test disks from guest'
        for pv in $(virsh domblklist guest | grep ^hd | \
            grep -v hda | awk '{print $1}')
        do
            virsh detach-disk guest ${pv} --persistent
        done
        
        # delete disk images:
        
        echo 'Deleting test disks'
        for img in $(virsh vol-list default | grep guest- | awk '{print $NF}')
        do
            virsh vol-delete ${img} default
        done
        
        # recreat test disks
        
        echo 'Recreating test disks'
        for x in 1 2
        do
            virsh vol-create-as default guest-${x}.img 10g
        done
        
        # attaching test disks to guest:
        echo 'Attaching test disks to guest'
        virsh attach-disk guest /var/lib/libvirt/images/guest-1.img hdb --persistent
        virsh attach-disk guest /var/lib/libvirt/images/guest-2.img hdc --persistent
        
        # restart guest
        
        echo 'restart guest'
        virsh start guest