[Linux-cluster] Oracle on a two node cluster: which filesystem ?

Greg Forte gforte at leopard.us.udel.edu
Tue Feb 14 13:02:37 UTC 2006

I have this exact same setup, and concluded that GFS would be less
trouble overall (though that conclusion is still open to re-evaluation
;-)  The problem, as I see it, is that if have your "shared" data on an
ext3 filesystem, then you want to make damn sure that the "failed" node
has unmounted (or simply ceased accessing) that filesystem before the
"backup" node mounts it and takes over the services.  If you have
hardware fencing then this is theoretically not a big problem, because
the failed node should get power cycled - but that's a BIG "should", and
there could be instances in which you want to switch the services over
without power cycling the "failed" node.  Forcing an unmount of an ext3
filesystem is dicey at best, and I just envisioned too many scenarios in
which both nodes ended up having the filesystem mounted simultaneously
and stomped all over the data.

So, the short version is: GFS is designed for this sort of thing, ext3
isn't.  BTW, LVM and GFS certainly aren't mutually exclusive.  I'm using
GFS/LVM with my SAN because the 'optimal' setup with the unit is to have
two separate raid5 stripes (because of the reserved area for the SAN OS
on some, but not all, of the disks), but I still wanted all of the
available space in one big chunk.  As to resizing a GFS filesystem:



Weyns, Frank wrote:
> Hi,
> I'm building a two node HA oracle cluster on Redhat. (One active
> production node and a stand-by node with a test application, which can
> be shutdown if needed. local system disks, stroage on SAN)
> The question is:
> Which underlying Filesytem to use ?
> We would prefer to use LVM with ext3 (stable , resize if needed,
> experience and knowledge in house)
> But everybody seems to use GFS:
> Why ?
>  What are the advantages to LVM-ext3 ?
> and
> If we use GFS, what are the things to keep in mind ? 
> /Frank Weyns
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