Re: active-pasive cluster in linux
- From: LS Cheng <exriscer@xxxxxxxxx>
- To: "Mark W. Farnham" <mwf@xxxxxxxx>
- Date: Tue, 23 Feb 2010 20:23:52 +0100
That is my point even mounting and dismounting filesystems is doable do we
really want to do it working with a clustering software which does not know
about filesystems except his own "filesystem" which is ASM? That is why I
said ASM is a must if we want to use Oracle Clusterware to setup an
active-passive cluster.
Thanks
--
LSC
On Tue, Feb 23, 2010 at 7:08 PM, Mark W. Farnham <mwf@xxxxxxxx> wrote:
> Most ports support a read only mount of a volume mounted read/write on
> one node. The only wrinkle I’ve noticed is that the appearance of new
> objects on the non-rw node may be slightly delayed. I’m uncertain of the
> exact mechanism of this delay, and it may vary by port.
>
>
>
> An interesting application of this is mounting all the log directories
> (both archived redo and diagnostic) as read only without the need for
> clustering software at the file system level. (They still have to be
> shareable volumes, of course). IF you’re not storing online redo in ASM this
> can also be used for the online redo logs, but of course you need the
> dbfiles multi-rw-able for any flavor of RAC. But this thread isn’t really
> about RAC.
>
>
>
> Purely for the active-passive idea, this of course means you can tail files
> on read mounted volumes and see the dying diagnostics from a crashed node
> without waiting for some other node to start or waiting to mount the
> volumes. Then you have the last messages at hand if you want to look at them
> before you activate the passive node. This can save a lot of time if the
> logs are telling you about, for example, media failure or some other issue
> that will just be repeated on the passive node.
>
>
>
> Presumably the interest in this type of architecture is minimizing the time
> until the applications are available on the passive node if the active node
> is in some sort of failure, as well as for routine planned switchover for
> preventive maintenance and just to prove it will work.
>
>
>
> <I wrote too much. I just wanted to introduce the notion about
> non-corrupting read only mountablility even without a clustered file system;
> David is absolutely correct you don’t want multiple concurrent rw mounts
> without a clustered file system, even if you can trick the OS into doing it
> for you.>
>
>
>
> mwf
> ------------------------------
>
> *From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
> oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *David Ballester
> *Sent:* Monday, February 22, 2010 6:26 PM
> *To:* LS Cheng
> *Cc:* jcmiranda@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
> *Subject:* Re: active-pasive cluster in linux
>
>
>
>
>
> 2010/2/22 LS Cheng <exriscer@xxxxxxxxx>
>
> Hi
>
> You can use OCFS2 if you wish but basically you need some sort of Cluster
> Filesystem or Volume Manager such as ASM.
>
> I dont mention OCFS2 because introducing two clustering software (OCFS2 and
> CRS) for a Single instance Active Passive solution is a bit too much in my
> opinion that is why I said you are forced to use ASM (runs on top of CRS).
>
> Thanks
>
>
>
>
> Or not use ocfs2 or any cluster filesystem, the only node that needs to
> have mounted the filesystems is the active one
>
> If you try to mount a non cluster filesystem in another node while is
> mounted in a first one, the other node should answer 'partition used' or
> something similar ( prevents corruption )
>
> when switching from nodes, as part of the automatic process, one node
> should umount and the other mount ( may be fsck first )
>
>
> Regards
>
>
> D.
>
>
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