[Linux-cluster] Multipathing, CLVM and GFS

Christine Caulfield ccaulfie at redhat.com
Mon Jul 28 07:58:41 UTC 2008

Sajesh Singh wrote:
> Christine Caulfield wrote:
>> Sajesh Singh wrote:
>>> Centos 4.6
>>> Cluster Suite
>>> I am currently running a 2 node GFS cluster. The storage is provided 
>>> via a fiber channel connection to the SAN. Each node currently has  a 
>>> single FC connection to the SAN. I would like to migrate to using 
>>> dm-multipath with each node having dual fiber channel connections to 
>>> the SAN. Can I assume that CLVM is aware of the /dev/dm-# devices 
>>> that are used to access the multipathed devices? Are there any 
>>> gotchas that are associated with installing the 
>>> device-mapper-multipath software after the GFS cluster is up and 
>>> running? Are there any howtos available for this type of setup?
>> clvmd works fine with dm-multipath devices. You will probably have to 
>> edit /etc/lvm/lvm.conf to exclude the underlying /dev/sd devices to 
>> stop it getting confused though.
>> You won't be able to do this with GFS mounted on the local node 
>> though, you'll have to umount it, setup dm-multipath, vgscan & 
>> remount. You CAN leave them mounted on other nodes while you do it.
> Christine,
>             Should clvmd be restarted as well so that I can create new 
> volume groups? I have device-mapper-multipath setup, but if I try to run 
> pvcreate /dev/mapper/mpath1p1 the command just hangs without any errors.

No, you shouldn't need to restart clvmd unless you have an old version 
and have added or removed PVs (which might be the case if you have 
changed multipath devices).

pvcreate does very little in the way of cluster operations so it's 
probably worth checking it's not stuck writing to the dm device.

(sorry for the delay in replying, I've been away).



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