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Re: [Linux-cluster] LVM2 cluster safety



On Tue, 9 Oct 2007, Darryl Dixon - Winterhouse Consulting wrote:

I'm trying to understand from the sourcecode and from previous discussions
on this list exactly which parts of a 'standard' LVM2 setup are 'unsafe'
in an active/active GFS or OCFS cluster scenario.

In other words, if I have a single LV, in a single VG, on a single PV, on
a single LUN seen by two hosts via an FC SAN, with GFS or OCFS on top of
it, and both hosts writing data, and no changes to the VG metadata at all,
then where are the points of risk?

From what I can understand of the CLVM daemon, it is entirely concerned
with serialising ~metadata~ updates, and writes to the LV are assumed to
be safe as long as they are going through a cluster-aware filesystem on
top?

My understanding that LVM is not required for clustering, unless you plan to grow the FS across multiple volumes. I am not aware of it having a functional effect on the functioning of GFS (other than the fact that it may need special features to make sure that it is GFS safe).

Gordan


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