On Mon, May 21, 2012 at 5:40 PM, Ian Latter
<address@hidden> wrote:
But they include an assumption.
The query is: are async writes and reads sequential? The
two specific cases are;
1) Are all reads that are initiated in time after a write
guaranteed to occur after that write has taken affect?
Yes
2) Are all writes that are initiated in time after a write (x)
guaranteed to occur after that write (x) has taken
affect?
Only overlapping offsets/regions retain causal ordering of completion. It is write-behind which acknowledges writes pre-maturely and therefore the layer which must maintain the 'effects' for further reads and writes by making the dependent IOs (overlapping offset/regions) wait for previous write's actual completion.
Avati