[linux-lvm] A couple of questions on locking library
zkabelac at redhat.com
Fri May 31 08:38:18 UTC 2019
Dne 31. 05. 19 v 9:13 Shawn Guo napsal(a):
> Hi David, Zdenek,
> Comparing to stable-2.02 branch, I noticed that there are significant
> changes around locking infrastructure on master branch. I have a
> couple of questions regarding to these changes.
> 1. I see External Locking support was removed as part of clvmd
> removal. What's the reason for dropping External Locking support? I'm
> asking because we are investigating the possibility to use hardware
> assisted locking for cluster, in form of External Locking extension.
> 2. It seems there have never been real support for LV (Logic Volume)
> locking. On stable-2.02 branch, the LV locking interface is used as
> activation path instead of real locking on LV. And on master branch,
> activation path gets separated off from locking infrastructure. As
> the result, the LV interface is dropped completely from locking
> infrastructure. My question is why there have never been LV locking
> support. Is the LV locking support an invalid requirement at all? Or
> it's just because no one cares about it enough to add the support?
> Thanks for your time, and appreciate any comment you would give here.
With stable-2.02 branch - there was always per-LV locking.
The 'state' of the LV was matching state of lock.
See the 'DLM – Distributed Lock Manager'
The lock however was always took only for top-level LV - never for those
There is however believe, that users no longer use volumes with shared
activation (active at one time on multiple hosts) - so lvm2 is now being moved
transformed to theoretically less complex locking scheme...
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