Re: Weird XFS WAL problem

Bruce Momjian <bruce@momjian.us> wrote:
> Kevin Grittner wrote:

>> The controller waits for the drive to tell it that it has made it
>> to the platter before it discards it.  What made you think
>> otherwise?
>
> Because a write-back drive cache says it is on the drive before it
> hits the platters, which I think is the default for SATA drive.
> Is that inaccurate?

Any decent RAID controller will ensure that the drives themselves
aren't using write-back caching.  When we've mentioned write-back
versus write-through on this thread we've been talking about the
behavior of the *controller*.  We have our controllers configured to
use write-back through the BBU cache as long as the battery is good,
but to automatically switch to write-through if the battery goes
bad.

-Kevin