Re: dm-cache issue

Teodor Milkov <tm@xxxxxx> · Fri, 2 Dec 2016 21:49:19 +0200



    So, I ended up with the following setup:

    
      Modified /etc/init.d/lvm2 to explicitly deactivate logical
        volumes: lvm lvchange -a n --select name=~.*
      
        Create /lvm2-clean-shutdown if
          deactivation is successful.
      
      Turn off automatic LV activation by setting auto_activation_volume_list=[]
        in /etc/lvm/lvm.conf
      Try to activate LVs later in the boot only if /lvm2-clean-shutdown
        exists.
    
    This way I have the chance to try manual activation of the
      volumes in the case of unclean shutdown, or eventually uncache and
      recreate caches if flush/refresh appears to take too much time.
    One strange thing is that while testing I forgot to set auto_activation_volume_list=[]
      and boot process got stuck at an very early stage –
      probably at udev activating lvm (/sbin/lvm
        pvscan --cache --activate ay from /lib/udev/rules.d/69-lvm-metad.rules).
      I waited for about five minutes but it didn't look like it's going
      to finish anytime soon, and I had no tty (too early in the boot),
      so I did reboot with a rescue CD and turned off LV auto activation
      in lvm.conf. This time the system came up quickly and the odd
      thing is that manual lvchange -ay was pretty fast - less
      that a minute for all 12 × 60GB caches. So, maybe there's a bug in
      udev/pvscan --activate?
    Anyway, the above setup seems to work well for me, so I'm
      sticking with it for the time being.
    Best regards,

      Teodor

    
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