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Re: [linux-lvm] Running LVM on shared LUNs



On Monday 07 August 2006 03:59pm, Joshua Aune wrote:
> I have two systems that are connected to a SAN.  The SAN is exporting
> the same 4 luns to each system (/dev/sd[b,c,d,e]).  Under normal
> operation system1 will combine sdb with sdc into a vg and system2 will
> combine sdd with sde into a vg with both vgs consisting of one large lv
> and one small lv.  After the system is configured there will be no
> modifications made to the LVM configuration.  LVM is configured on one
> node and then copied over to the second node.
>
> The million dollar question is, can system1 and system2 simultaneously
> have both of the VGs active without hosing any data?

As I understand it, only if you are using a filesystem that supports clustered 
operations, like GFS.

> I am not trying to have the same filesystem mounted simultaneously, just
> have the LVs available simultaneously for failover needs

In that case, as long as you have some heartbeat or something that lets you 
know when the one system needs to take over the other's PVs.  The trick here 
is that if you lose your network connection, but the box is still accessing 
data on the LUNs, that could become problematic.  Maybe a tiny little shared 
GFS thing would allow your boxes a place to write some status info (a 
custom "heartbeat", if you will) so that a network disconnect or other issue 
won't cause false alarms.

Probably best to just use GFS.

> I know that this sort of config can be done with the GFS pool volume
> manger but I have been told that many other VMs don't support this
> behavior....

/me shrugs

Not sure about that as I don't have any SAN to play with :( .  Never tried it.
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Lamont R. Peterson <peregrine OpenBrainstem net>
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