org.postgresql.util.PSQLException: PANIC: could not write to log file

In our customer site, the following error occurred. I tried to find some
indication what this means. Is this log file used for the roll back
purpose? In what scenario that one gets such fatal error?

Please help!!!

Mzhang

Caused by: org.jboss.resource.JBossResourceException: SQLException; -
nested throwable: (org.postgresql.util.PSQLException: PANIC: could not
write to log file 6, segment 176 at offset 14991360, length 8192:
Read-only file system)
at
org.jboss.resource.adapter.jdbc.BaseWrapperManagedConnection.checkException(BaseWrapperManagedConnection.java:636)
at
org.jboss.resource.adapter.jdbc.local.LocalManagedConnection.commit(LocalManagedConnection.java:73)
at
org.jboss.resource.connectionmanager.TxConnectionManager$LocalXAResource.commit(TxConnectionManager.java:905)
... 23 more
Caused by: org.postgresql.util.PSQLException: PANIC: could not write to
log file 6, segment 176 at offset 14991360, length 8192: Read-only file
system
at
org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1525)
at
org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1309)
at
org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:188)
at
org.postgresql.jdbc2.AbstractJdbc2Connection.executeTransactionCommand(AbstractJdbc2Connection.java:617)
at
org.postgresql.jdbc2.AbstractJdbc2Connection.commit(AbstractJdbc2Connection.java:637)
at
org.jboss.resource.adapter.jdbc.local.LocalManagedConnection.commit(LocalManagedConnection.java:69)
... 24 more