> -----Original Message----- > From: fio-owner@xxxxxxxxxxxxxxx [mailto:fio-owner@xxxxxxxxxxxxxxx] On Behalf Of Left Right > Sent: Wednesday, May 1, 2019 10:06 PM > To: fio@xxxxxxxxxxxxxxx > Subject: How do reads and writes overlap? > > I was looking for this info, online, but with no luck so far. What I'm > really interested to know is this: > > * Say, you have a mixed sequential workload 75% reads, 25% writes with > queue depth greater than one, then: > ** are all writes executed before all reads? No. > ** are there any reads from the blocks not yet written to? Yes. > ** are there any reads performed against writes that are not ack'ed yet? Yes. > ** are there any writes performed to the same blocks that have a > pending read request? Yes. > * Does any of the answers change if we modify the ratio of reads to > writes, sequential to random? No. Remember that fio is a primarily a workload generator, not a data validation tool. It doesn't care what data it gets back from reads (comparing all the bytes would take too much time, interfering with performance). You can run special verify threads, but those are separate from the normal read workloads.
