[linux-lvm] LV mirror extents on same physical device

[Roger Heflin]

If I am reading what I can find correctly - -alloc=anywhere defeats
the mirror code from attempting to put on 2 different physical
devices.

The man pages seem to lack info on what other values there are for
that but disables device mirroring.

On Sat, Feb 22, 2014 at 1:14 AM, Julie Ashworth <ashworth at berkeley.edu> wrote:
> hi all,
>
> just some background...
> I installed a CentOS5 server in 2010 with a mdadm RAID1 containing 2 partitions (/dev/sda1 and /dev/sdb1). /dev/sda1 failed, and unfortuately, the mirror failed to sync with a new drive.
>
> On this RAID1, I have one VG (VolGroup00) with 5 LVs.
>
> I contacted the folks on the mdadm mailing list. The data on /dev/sdb is good, so they recommended that I convert the linear LVs to mirrors (to copy the data to a new drive).
>
> I formatted a new drive (/dev/sde) identical to /dev/sd[ab], added it to a mdadm device (/dev/md2), which I then added to my VG:
> mdadm --create --level=1 -n 2 /dev/md2 /dev/sde2 missing
> pvcreate /dev/md2
> vgextend VolGroup00 /dev/md2
>
> I then converted all my volumes to mirrors:
> lvconvert -m1 --mirrorlog=mirrored --alloc=anywhere /dev/VolGroup00/srvlv
> lvconvert -m1 --mirrorlog=mirrored --alloc=anywhere /dev/VolGroup00/rootlv
> lvconvert -m1 --mirrorlog=mirrored --alloc=anywhere /dev/VolGroup00/swaplv
> lvconvert -m1 --mirrorlog=mirrored --alloc=anywhere /dev/VolGroup00/varlv
> lvconvert -m1 --mirrorlog=mirrored --alloc=anywhere /dev/VolGroup00/tmplv
>
> (in case you're wondering, when this completed, I added /dev/sda1 to /dev/md2, so /dev/md2 is a fuctional mdadm RAID1).
>
> Now... the problem ;)....
>
> When I run 'lvs' I see that the LV mirror extents were created on the same device (/dev/md1):
>
> # lvs -a -o +devices
> LV                     VG         Attr   LSize  Origin Snap%  Move Log         Copy%  Convert Devices
> rootlv                 VolGroup00 mwi-ao 10.00G                    rootlv_mlog 100.00         rootlv_mimage_0(0),rootlv_mimage_1(0)
> [rootlv_mimage_0]      VolGroup00 iwi-ao 10.00G                                               /dev/md1(0)
> [rootlv_mimage_1]      VolGroup00 iwi-ao 10.00G                                               /dev/md1(4036)
> [rootlv_mlog]          VolGroup00 mwa-ao 32.00M                                100.00         rootlv_mlog_mimage_0(0),rootlv_mlog_mimage_1(0)
> [rootlv_mlog_mimage_0] VolGroup00 iwi-ao 32.00M                                               /dev/md2(4)
> [rootlv_mlog_mimage_1] VolGroup00 iwi-ao 32.00M                                               /dev/md1(4356)
>
>
> My long-term goal is to convert the mirror back to a linear volume using just /dev/md2, i.e.
> lvconvert -m0 /dev/VolGroup00/rootlv /dev/md1
> lvconvert -m0 /dev/VolGroup00/swaplv /dev/md1
> lvconvert -m0 /dev/VolGroup00/srvlv /dev/md1
> lvconvert -m0 /dev/VolGroup00/varlv /dev/md1
> lvconvert -m0 /dev/VolGroup00/tmplv /dev/md1
>
> ... so it seems problematic that both extents are on /dev/md1.
>
> I thought lvm was supposed to use both physical devices. Do you know why both extents were created on the same physical device?
> Should I create another extent on /dev/md2 before I remove the /dev/md1 extent(s)? If so, can you give me an example of how to use lvconvert in this case?
>
> Thanks in advance!
> best,
> Julie
>
>
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