Re: [linux-lvm] Docs on clustered option of vgcreate

[Patrick Caulfeld <pcaulfie redhat com>]

Gerrard Geldenhuis wrote:
> Excellent, thanks for the answer, that makes it a lot clearer.
> 
>  
> 
> So coupled with exclusion lists etc.. I could have multiple machines
> connect to one LUN and each have its own logical volume. Is there a
> concept of a “master” in the cluster or does it work in the same way as
> tcp with an exponential backoff when the metadata is locked by a host
> for changing. I am assuming that cluster aware locking would allow
> server-a to create a new lv but not simalteneosly allowing server-b to
> create a new lv too.
> 
>  
> 
> I know should be experimenting with this but will ask in the mean time
> while I wait for my “test lun”.
> 
>  
> 
> If host A creates a lv on a shared storage will it automatically be
> marked as only belonging to host A or is that something you have to do
> by hand. I read somewhere in the man pages about tags that you need to
> add to achieve such things.
> 


Locking in CLVM is exclusive and there's no back off. There is no reason
for it, creating an LVM doesn't take very long and is done from a
command-line. Host 'b' will simply wait until host 'a' has finished its job.

If you need to mark LVs to be exclusive to a node you will need to use
tags to define which node is allowed access