[ovirt-users] LVM structure

[Nicolas Ecarnot]

Adam,

TL;DR : You nailed it!

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