[linux-lvm] Cloning Logical Volumes
jed at nersc.gov
Tue May 2 00:05:01 UTC 2006
At 03:21 PM 4/27/2006, Jonathan E Brassow wrote:
>dd is probably the best way right now.
>in the future, the clone would probably take the form:
>prompt> lvconvert -m1 vg/lv; (wait for sync); lvsplit vg/lv
>The syntax isn't worked out yet and lvsplit is not there yet... but
>we have talked about doing something like that.
One possibility that occurs to me is to use RAID-1 under LVM and then
clone your LVM file system(s)
by splitting a software RAID-1 clone (e.g. MD driver). Even if you
don't want to pay the price of redundant
disks in your final system configuration, you can leave it with a
single 1/2 RAID set with no loss of reliability
(over no RAID). You can even do the RAID-1ing on a single disk if
that has any potential value, but it's a bit
more difficult for me to see how you would separate the clone out that way.
Just a thought. I use such RAID-1 cloning quite often and find it
very convenient. It seems to me it
would work fine in this case. About the only thing I find I have to
be careful of is to be sure that if
I'm cloning the /boot (or /root if it includes /boot) file system
that I make sure the boot record is in
place (in my case running grub and writing the appropriate record on
the appropriate disk before
splitting the RAID system for cloning).
I still don't trust LVM for recovering munged file systems (no
effective mechanism for fsck if you
can't get to the LVM file system, init problems for RAID-10, etc. as
mentioned previously on
this list) so I'm not using LVM at this time and haven't tested the
above mechanism. You're
mileage may vary.
>On Apr 26, 2006, at 5:55 PM, Greg Hartzog wrote:
>>Hello there folks. I have a question.
>>I am looking for a better way of cloning logical volumes then
>>creating a new logical volume, identical to a source logical
>>volume, and using "dd" to copy data between the two logical volumes.
>>I would love to use dm-mirror to do this, but I do not think any
>>interface has been provided to do this yet.
>>All suggestions and ideas appreciated.
>>I am running lvm2-2.02.04-r1 & 2.6.15 kernel.
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