Re: Converting thin stripe volume to linear

[Zdenek Kabelac <zdenek.kabelac@gmail.com>]

Dne 13. 03. 25 v 1:38 Patrick Hemmer napsal(a):
> I've got a LVM thin stripe volume across 2 drives that I'm trying to migrate to a new larger single drive (getting rid of the old drives). Following various information on the subject, it seems the procedure here is to first convert from stripe to mirror, and then from mirror to linear. While attempting this, I seem to have hit an issue on the second part of that process, and am not having much luck resolving it.

Hi

Likely you can convert your nearly full thin-pool with a single thin volume to 
a linear  LV by just taking  'dd' copy of  if=/dev/thin of=/dev/linear - using 
direct io option (and this can be actually faster then raid mirroring).

If you are converting _tdata - you are basically using raid1 for _tdata - but 
that is no help to convert anything to linear - _tdata holds 'chunks' and how 
these chunks are 'mapped' to 'create' your thinLV looking like a 'linear block 
device' is fully in control by a thin-pool target and the use of _tmeta content.

While lvm2 could eventually add support doing a raid for thinLV - so you can 
have your duplicate made while your device is online and in-use - currently 
there is no such variant support - so you need to  'activate'  thinLV
and without any use/mounting take a  'dd' copy.

> 
> Any idea how I get past this point? I could just build a completely new logical volume and manually copy the data, but there's around 40 logical volumes on this thin pool, many of which are snapshots, so would be much easier to just convert it if possible.

Well once you go to thin-pool, there is no other route to go back to linear 
other then 'manual copy' (and no one has even requested such feature).

Regards

Zdenek