Ext3 users - Mar 2009 - SAN partition with ext3 fs turns read only when shared bet two servers

Dear All,

Scenario:

I am facing a unique issue as below. I have two physical machines installed
with a windows beta virtualization env. on them. There is one centos 5.2
virtual server running on each physical machine. There is a SAN (IBM)
partition provided to the virtualized servers by the host Windows OS on both
physical machines. The partition is formated in ext3  Both the virtualized
Centos servers are linked using heartbeat so that any of the server goes
down the other server will take on the resources (Namely a floating IP and
SAN storage) and start the services so that there is minimal interruption in
services during hardware failure of one server. This is similar to heartbeat
with drbd sans drbd. We have imap user data mounted on the system as since
we had  a SAN storage didnt opt for internal Storage or drbd structure.

Graphical Representation is attached for elaboration.

Problem: The problem is that during the fail over testings we found that the
ext3 partition became read only during transition from one server to other
server.  What i want to know is

1. if attached scenario is feasible where in during failover occurs the
other server mounts the SAN storage and mailbox server is available at all
time.
2. What happens when one server has network issue but has not unmounted the
SAN ? Is this the case why probably my partition becomes read only?

regards,
Ashay.
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Ashay Chitnis wrote:
> Dear All,
> 
...
> 2. What happens when one server has network issue but has not unmounted
> the SAN ? Is this the case why probably my partition becomes read only?
then you have 2 systems writing to the same block device with no
coherency between them, which will corrupt the filesystem, and one
system or the other or both will eventually notice this, throw an error,
and go readonly (if you have errors=ro).

You'll need to do something like STONITH (shoot the other node in the
head) before the new node can safely take over.

-Eric