[linux-lvm] Raid1 -> linear conversion = destroyed data

[Jason Warr]

On Wed, 10 Dec 2014 19:15:05 -0600, Phillip Susi <psusi at ubuntu.com> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> On 12/08/2014 03:59 PM, Jason Warr wrote:
>> I may have missed part of the discussion but in order to fully
>> understand what is going on I'd like to know what arguments you
>> used when you issued the "lvconvert --splitmirrors" command.  There
>> are several options to it that can influence what happens to the
>> mirror members.
>
> The exact sequence of commands was:
>
> lvconvert --type raid1 -m 1 faldara/utopic /dev/sdb1
> lvconvert --splitmirrors 1 --trackchanges faldara/utopic --name
> utopic-backup /dev/md0

It ignores the name because what it does with "--trackchanges" is rename  
the mirror leg to a visible & read only version of the meta.  Sample:

[5:root at goldmember /etc/sysconfig/network-scripts]# lvs -a -o  
lv_name,lv_attr,lv_dm_path,devices,copy_per
   LV                  Attr       DMPath                                  
Devices
   test01LV            rwi-aor--- /dev/mapper/test01VG-test01LV           
test01LV_rimage_0(0),test01LV_rim
   [test01LV_rimage_0] Iwi-aor--- /dev/mapper/test01VG-test01LV_rimage_0  
/dev/sdas(12802)
   [test01LV_rimage_1] Iwi-aor--- /dev/mapper/test01VG-test01LV_rimage_1  
/dev/sdar(12802)
   [test01LV_rmeta_0]  ewi-aor--- /dev/mapper/test01VG-test01LV_rmeta_0   
/dev/sdau(0)
   [test01LV_rmeta_1]  ewi-aor--- /dev/mapper/test01VG-test01LV_rmeta_1   
/dev/sdat(0)

Would be like so after:

[5:root at goldmember /etc/sysconfig/network-scripts]# lvs -a -o  
lv_name,lv_attr,lv_dm_path,devices,copy_per
   LV                  Attr       DMPath                                  
Devices
   test01LV            rwi-aor--- /dev/mapper/test01VG-test01LV           
test01LV_rimage_0(0),test01LV_rim
   test01LV_rimage_0   Iri-a-r--- /dev/mapper/test01VG-test01LV_rimage_0  
/dev/sdar(1)
   [test01LV_rimage_1] iwi-aor--- /dev/mapper/test01VG-test01LV_rimage_1  
/dev/sdas(12802)
   [test01LV_rmeta_0]  ewi-a-r--- /dev/mapper/test01VG-test01LV_rmeta_0   
/dev/sdar(0)
   [test01LV_rmeta_1]  ewi-aor--- /dev/mapper/test01VG-test01LV_rmeta_1   
/dev/sdas(12801)



> lvconvert --splitmirrors 1 --trackchanges faldara/utopic --name
> utopic-backup /dev/md0
>
> The idea was to start using the new drive exclusively while keeping a
> backup on the old drive.
>
> Also I thought it was a bit odd that --splitmirrors accepted the
> - --name argument, but silently ignored it, instead using an internal
> auto generated name.
>

You can't track changes and rename the "backup" leg at the same time.  If  
you wanted to keep the backup leg after making sure the in use one was  
good you would need to issue a new "--splitmirror"
  command with a new volume name and *no* "--trackchanges" option.

>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1
>
> iQEcBAEBCgAGBQJUiPAZAAoJENRVrw2cjl5RAS0H/10hFYNUF8n71iXER0iQVAtd
> bHauiQBbemml3Q1RgqWHCFj2SYQB0epACFHIdyDUC2kWaNyQ7A9VnbRPsnyEGLzo
> Tu2+LjbH2QA1e8J9zHQYq8BO0jHay5n/1S/JZrhUHxW0hyI3vnsVXESNA4GUntqn
> tcC7N+wzu8SUIuqjtcm30kEE0ZvzlDv4znADIudJzXJu7JE+TjhIljg5YWY8NBxE
> AYbUc1f8tGKzIyzehPETpq6/Hsi4C8C27nw+kugs+HvrmWO29nqhjQczXlbYfvjL
> SDNsXLMj68dkjSqJzuuK0jy6HlHgrPxJJtaGfJ92TIcFbm9gVJHWfqClzbd1vao=
> =am39
> -----END PGP SIGNATURE-----
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/