[Linux-cluster] fencing node and filesystem

[Rajagopal Swaminathan]

Greetings,

On Mon, Feb 8, 2010 at 8:19 PM, Bob Peterson <rpeterso at redhat.com> wrote:
> ----- "Muhammad Ammad Shah" <mammadshah at hotmail.com> wrote:
> | when a node(x) fenced by another node(y), will it corrupts the file
> | system or no? and if the database was running and node(x) fenced by
> | fenced node(y) will it corrupts the database or whats about the
> | transaction ?
>
> With GFS and GFS2 there should be no metadata corruption, in theory.
> When quorum is regained (or if it's not lost) the fenced
> node's journal is replayed so the file system metadata should
> remain intact.  That does not mean that data won't be lost.
> If the node was fenced while it had data in its cache, that data
> may be lost.  In critical situations, you can mark files and/or
> directories with a flag that makes the data journaled as well,
> so the data should be protected.  Of course, that has a performance
> penalty.  There's a small section about this in the GFS faq.

Whatever Rob says is absolutely correct.

Having said that, IIRC DBs like Oracle writes to disks every 3 seconds
and Linux flushes to disk every five seconds anyways.

So, one can say that the the data loss window could be at most 5
seconds. Am I right?

Thanks and regards,

Rajagopal