> I have a question on why the ZNS write behavior does not match > the read behavior. In write workloads with an offset that > results in a starting lba that is not on a zone boundary, > the offset is rounded up to the next zone starting lba. This is > not done for read workloads though. I'd like to know if there is > a particular reason why or could I change this behavior to be > the same for both reads and writes. The root cause, so to speak, is that fio tries to be nice and accomodating program and doesn't reject offsets unaligned to zone boundaries. Unlike floating point where there is natural "round to nearest" rounding mode zoned I/O does not have that property. There are three ways a) reject unaligned offset= b) accept unaligned offset= but reject first I/O if write pointer is different this allows the following workload to work, at least conceptually zonemode=zbd [a] rw=write io_size=4096 [b] rw=write offset=4096 io_size=4096 c) round down(!) this is natural given that zoned writes are "rounded down" to the WP fio does none of the above. > This causes a problem for one of our particular testcases that writes > a particular pattern at an offset that ends up being rounded up > to the next zone starting lba. In the 2nd step of this testcase, a read > with verify workload is done to verify the write workload. This fails > with a miscompare because the read workload is not starting at the same > offset as the write workload. Both fio workloads have "offset = 1%". I think the best you could do it to fill the zone up the LBA and then creates separate job which writes pattern and immediately verifies it. [a] rw=write io_size=4096 offset=2z size=1z [b] stonewall rw=write io_size=4096 offset=2z size=1z verify=xxhash do_verify=1 Note! Mainline fio supports 'z' suffix, which is much better than percentages!
