Write cache / barrier

Write cache / barrier

[John K Luebs]

I'm using md devices. What I don't understand is how things with the
raid are kept safe when write caching is enabled on the underlying
devices. Forgetting filesystem integrity, if a write access hits
one of the disks and the power goes out, won't the members of the array
be inconsistent without the md layer knowing about it?

For now I am running with write caching turned off.

Also, some drives support write cache flushing and some do not. Does
this make any difference to md?

 Thanks,
   -jkl