[linux-lvm] export/migrate - but only a LV - how?

[linux-lvm] export/migrate - but only a LV - how?

[lejeczek]

.. if possible?

hi users,

I'd like to ask, while reading different docs, whether it's 
possible to migrate/export just a LV?

What I'm hoping to achieve is to take a LV out of a VG and 
move it over to another system so a can restore that LV and 
carry on using it, while having a reduced VG on original, 
source system.

I see there some docs tell how to do a VG, how only a LV can 
be migrated?

many thanks

Re: [linux-lvm] export/migrate - but only a LV - how?

[Brassow Jonathan]

maybe pvmove the LV to a unique device and then vgsplit?

 brassow

> On Jul 12, 2016, at 10:23 AM, lejeczek <peljasz@yahoo.co.uk> wrote:
> 
> .. if possible?
> 
> hi users,
> 
> I'd like to ask, while reading different docs, whether it's possible to migrate/export just a LV?
> 
> What I'm hoping to achieve is to take a LV out of a VG and move it over to another system so a can restore that LV and carry on using it, while having a reduced VG on original, source system.
> 
> I see there some docs tell how to do a VG, how only a LV can be migrated?
> 
> many thanks
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] export/migrate - but only a LV - how?

[Xen]

Brassow Jonathan schreef op 18-07-2016 17:50:
> maybe pvmove the LV to a unique device and then vgsplit?
> 
>  brassow
> 
>> On Jul 12, 2016, at 10:23 AM, lejeczek <peljasz@yahoo.co.uk> wrote:
>> 
>> .. if possible?


Shouldn't you in general just recreate the LV with the same amount of 
extents and then perform a DD?

I realize an atomic move operation for an LV could conceptually be nice 
but apart from the mental effort required to do this recreation 
manually, there is not much practically in the way of doing it yourself.

In the end, it would be nothing more than a shell script doing an 
LVCREATE, DD, and LVREMOVE?

Regards.

Re: [linux-lvm] export/migrate - but only a LV - how?

[Brassow Jonathan]

> On Jul 18, 2016, at 3:28 PM, Xen <list@xenhideout.nl> wrote:
> 
> Brassow Jonathan schreef op 18-07-2016 17:50:
>> maybe pvmove the LV to a unique device and then vgsplit?
>> brassow
>>> On Jul 12, 2016, at 10:23 AM, lejeczek <peljasz@yahoo.co.uk> wrote:
>>> .. if possible?
> 
> 
> Shouldn't you in general just recreate the LV with the same amount of extents and then perform a DD?
> 
> I realize an atomic move operation for an LV could conceptually be nice but apart from the mental effort required to do this recreation manually, there is not much practically in the way of doing it yourself.
> 
> In the end, it would be nothing more than a shell script doing an LVCREATE, DD, and LVREMOVE?

One advantage is that pvmove allows you to keep the device online...  We are also working on a feature ATM called “duplicate”.  It allows you to create a duplicate of any LV stack, create the duplicate where you want, and even change the segment type in the process.  For example, you could move a whole RAID5 LV, or thin-p, in one go.

 brassow

Re: [linux-lvm] export/migrate - but only a LV - how?

[Xen]

Brassow Jonathan schreef op 22-07-2016 15:12:

> One advantage is that pvmove allows you to keep the device online...

Right, that is pretty advanced. Good going.


> We are also working on a feature ATM called “duplicate”.  It allows
> you to create a duplicate of any LV stack, create the duplicate where
> you want, and even change the segment type in the process.  For
> example, you could move a whole RAID5 LV, or thin-p, in one go.

I think one important "trouble spot" is that there is no operation 
yet(?) to create a duplicate of a PV that will not ruin the system 
unless you do pvchange -u and vgchange -u ;-).

It took quite a bit of time for me to realize what was going on ;-).

Is PVMOVE supposed to be a backup task? I don't think so? How are you 
supposed to back something up if you are planning to move your system to 
a new disk?