[linux-lvm] LV mirror extents on same physical device
ashworth at berkeley.edu
Sat Feb 22 07:14:08 UTC 2014
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
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!
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