[ovirt-users] LVM structure

[Adam Litke]

On Wed, Oct 4, 2017 at 4:12 AM Nicolas Ecarnot <nicolas at ecarnot.net> wrote:

> Adam,
>
> TL;DR : You nailed it!


Great!  Glad you're back up and running. One additional note about LVM
commands. It's dangerous to use lvmetad for some commands while vdsm is
running since it will not use lvmetad. You could end up with conflicting
operations. In general it's safest to not issue any lvm commands while the
host is activated but if you must, don't forget to disable lvmetad for all
commands.


>
> Le 03/10/2017 à 18:12, Adam Litke a écrit :
> > Does this report an error on the host where you are having problems
> > activating logical volumes?
> >
> >      lvs -a -o +devices
>
> On the hosts where I can't activate a LV, this command returns nothing
> interesting :
>
> root at serv-hv-prd03:~# lvs -a -o +devices
>    LV   VG Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync
> Convert Devices
>    home cl -wi-ao---- 56,25g
>          /dev/sda2(1024)
>    root cl -wi-ao---- 50,00g
>          /dev/sda2(15423)
>    swap cl -wi-ao----  4,00g
>          /dev/sda2(0)
>
> and so goes for pvs and vgs.
>
> >
> > Also, do the lvm commands succeed when you explicitly disable lvmetad,
> ie...
> >
> >      lvchange --config 'global {use_lvmetad=0}' -ay ...
>
> Disabling lvmetad usage allows the activation to succeed.
>
> Having understand that, I tried to run some usual LVM commands like pvs
> vgs, lvs, pvscan, vgscan, lvscan, lvmdiskscan, and they all returned
> some quite empty answers (to be short : only the local LV).
>
> Having understood the role of lvmetd, I ran pcscan --cache, and all in a
> sudden it filled up the LVM informations : I found back all my oVirt LVM
> storage domains, as I could see on other hosts.
>
> Things to note :
> - trying to run a VM on empty LVM cache was nonetheless successful
> - before filling the lvmetad cache, I checked this daemon was running
> and it was.
>
>
>
> --
> Nicolas ECARNOT
>
-- 
Adam Litke
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