Durability?

Hi,

I got an error like this:

ERROR:  xlog flush request 1/C121E998 is not satisfied --- flushed only to 1/BCBCB440
CONTEXT:  writing block 529 of relation 1663/233690/1247
WARNING:  could not write block 529 of 1663/233690/1247
DETAIL:  Multiple failures --- write error might be permanent.

The xrecoff value (logs show 1/xrecoff) advances a few times during the day, but the message keeps appearing.

I am not sure to understand clearly the consequences of such error since Postgres continues to accept new transactions.
Ifmy WAL is corrupted, are my transactions still durable?
 
If this is a violation of durability, is there a way to force Postgres to terminate on such error?

Thanks in advance for the clarification.
Emmanuel