[linux-lvm] lvm mirroring

[Roman Gavrilov]

Hello,

I have 2 physical discs.
I have 4 partitions on the first disk. 
I created a volume group "lvmhd" from all of the partitions and later created logical volumes.

this is the result from the vgdisplay
--- Volume group ---
VG Name               lvmhd
VG Access             read/write
VG Status             available/resizable
VG #                  0
MAX LV                256
Cur LV                3
Open LV               3
MAX LV Size           2 TB
Max PV                256
Cur PV                4
Act PV                4
VG Size               35.59 GB
PE Size               32 MB
Total PE              1139
Alloc PE / Size       1131 / 35.34 GB
Free  PE / Size       8 / 256 MB
VG UUID               xqamqE-9gSs-Xy3O-2tVQ-wYzy-Cp3u-0Wivbd

and those are the logical volumes
/dev/lvmhd/lvm_usr    3.0G  980M  1.8G  35% /usr
/dev/lvmhd/lvm_var    4.9G   65M  4.6G   2% /var
/dev/lvmhd/lvm_home    27G   33M   25G   1% /home

later I mirrored the first disk to the second disk with dd if=/dev/hda of=/dev/hdb so if the first disk breaks I can remove it and replace it with the second disk and get the server up in minutes.

Now I want to be able to use the second disk while I am running from the first. But the volume groups are the same and I am afraid that if I will recreate the logical volumes I'll ruin some thing on the second disk.
Is there anything I can do about it so I could use the second disk for backups but still have the same architecture as the primary disk ?
is there any way to mount those logical volumes which are mirrors of the primary disk ?
for example I can do 
pvdisplay /dev/hdb3 (this is the slave disk which is the mirror of the primary and its not mounted)
--- Physical volume ---
PV Name               /dev/hdb3
VG Name               lvmhd
PV Size               13.67 GB [28676025 secs] / NOT usable 32.19 MB [LVM: 129 KB]
PV#                   1
PV Status             available
Allocatable           yes (but full)
Cur LV                3
PE Size (KByte)       32768
Total PE              436
Free PE               0
Allocated PE          436
PV UUID               5XenPH-2NLb-cmN0-qEBb-QGuJ-zWxv-otMr7i

thanks
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