[Linux-cluster] lvm locking type 2, still used?

[rhurst at bidmc.harvard.edu]

With that said, the latest lvm2-cluster-2.02.21-7.el4
installs /etc/lvm/lvm.conf.rpmnew, with new locking_type definition(s).
It leaves the previous lvm.conf alone, which we did, and that is set to
#2.  I am not clear on the use of Type 3 -- does that mean there is a
static version, for like a ramdisk?  Which is preferable settings for a
'regular' cluster LVM with GFS?  Please advise, thanks.


    # Type of locking to use. Defaults to local file-based locking (1).
    # Turn locking off by setting to 0 (dangerous: risks metadata
corruption
    # if LVM2 commands get run concurrently).
    # Type 2 uses the external shared library locking_library.
    # Type 3 uses built-in clustered locking.
    locking_type = 1
...
    fallback_to_clustered_locking = 1
...
    fallback_to_local_locking = 1
...
    locking_dir = "/var/lock/lvm"


On Wed, 2007-05-30 at 15:31 +0100, Patrick Caulfield wrote:

> isplist at logicore.net wrote:
> > I am adding nodes and just noticed something interesting. When I started with 
> > GFS/Clustering, one of the requirements which I made a note of was having to 
> > modify the /etc/lvm/lvm.conf in the following manner for my RHEL4 machines;
> > 
> > locking_type = 2
> > and
> > locking_library = "/usr/lib/liblvm2clusterlock.so"
> > 
> > I just noticed that over time, this file was changed back to what it used to 
> > be by default which is;
> > 
> > locking_type = 1 
> > and 
> > locking_library path has been removed. 
> > 
> > This is not something I've done, it's happened over time, using yum to keep 
> > things up to date. Yet, the cluster works just fine and all volumes can be 
> > seen. Did I miss something about not needing to do this anymore?
> > 
> 
> 
> The locking is only really needed when you change LV metadata (lvcreate,
> lvextend etc). so if all you are doing is activating existing LVs then the
> missing locking will make little difference.
> 
> If you make any changes to LVs on a mode with the locking_type set incorrectly
> then those changes will not be visible on the other nodes. However, lvm2 is
> smart enough not to let you change clustered VGs when clvmd isn't available so
> it's unlikely to have caused any harm. you would have noticed something was
> wrong the first time you needed to change anything/
> 

Robert Hurst, Sr. Caché Administrator
Beth Israel Deaconess Medical Center
1135 Tremont Street, REN-7
Boston, Massachusetts   02120-2140
617-754-8754 ∙ Fax: 617-754-8730 ∙ Cell: 401-787-3154
Any technology distinguishable from magic is insufficiently advanced.
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