[ClusterLabs] HALVM problem with 2 nodes cluster

[Marco Marino]

Ferenc, regarding the flag use_lvmetad in
/usr/lib/ocf/resource.d/heartbeat/LVM I read:

        "#lvmetad is a daemon that caches lvm metadata to improve the
        # performance of LVM commands. This daemon should never be used when
        # volume groups exist that are being managed by the cluster. The
lvmetad
        # daemon introduces a response lag, where certain LVM commands look
like
        # they have completed (like vg activation) when in fact the command
        # is still in progress by the lvmetad.  This can cause reliability
issues
        # when managing volume groups in the cluster.  For Example, if you
have a
        # volume group that is a dependency for another application, it is
possible
        # the cluster will think the volume group is activated and attempt
to start
        # the application before volume group is really accesible...
lvmetad is bad."

in the function LVM_validate_all()
Anyway, it's only a warning but there is a good reason. I'm not an expert,
I'm studying for a certification and I have a lot of doubts.
Thank you for your help
Marco




2017-01-18 11:03 GMT+01:00 Ferenc Wágner <wferi at niif.hu>:

> Marco Marino <marino.mrc at gmail.com> writes:
>
> > I agree with you for
> > use_lvmetad = 0 (setting it = 1 in a clustered environment is an error)
>
> Where does this information come from?  AFAIK, if locking_type=3 (LVM
> uses internal clustered locking, that is, clvmd), lvmetad is not used
> anyway, even if it's running.  So it's best to disable it to avoid
> warning messages all around.  This is the case with active/active
> clustering in LVM itself, in which Pacemaker isn't involved.
>
> On the other hand, if you use Pacemaker to do active/passive clustering
> by appropriately activating/deactivating your VG, this isn't clustering
> from the LVM point of view, you don't set the clustered flag on your VG,
> don't run clvmd and use locking_type=1.  Lvmetad should be perfectly
> fine with this in principle (unless it caches metadata of inactive VGs,
> which would be stupid, but I never tested this).
>
> > but I think I have to set
> > locking_type = 3 only if I use clvm
>
> Right.
> --
> Feri
>
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