Jody McIntyre wrote:
We turn write caching off for data integrity reasons (write reordering does bad things to journalling file systems if power is interrupted - and at the scale of many Lustre deployments, it happens often enough to be a concern.) I'm also concerned about the effects of NCQ in this area so we'll probably turn it off anyway.
.. I haven't done a detailed examination lately, but.. Both write-caching and NCQ re-ordering should be safe on Linux. The kernel will issue FLUSH_CACHE_EXT commands as required to checkpoint data to the disk. Or at least that's how I understood Tejun's last explanation of it. It is possible that the drive firmware in some brands may not follow spec for FLUSH_CACHE_EXT, but I don't know of a specific instance of this. Cheers -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
