On Tue, 2018-07-10 at 08:46 -0600, Jens Axboe wrote: > On 7/9/18 6:05 PM, Bart Van Assche wrote: > > On Mon, 2018-07-09 at 10:34 -0600, Jens Axboe wrote: > > > In the spirit of making some progress on this, I just don't like how > > > it's done. For example, it should not be necessary to adjust what > > > comes out of the block generator, instead the block generator should > > > be told to do what we need on zbc. This is a key concept. The workload > > > should be defined as such that it works for zoned devices. > > > > How would you like to see block generation work? I don't see an > > alternative for random I/O other starting from the output of a random > > generator and translating that output into something that is > > appropriate for a zoned block device. Random reads must happen below > > the zone pointer if fio is configured to read below the zone pointer. > > Random writes must happen at the write pointer. The only way I see to > > implement such an I/O pattern is to start from the output of a random > > generator and to adjust the output of that random generator. However, > > I don't have a strong opinion whether adjusting the output of a random > > generator should happen by the caller of get_next_buflen() or inside > > get_next_buflen(). Or is your concern perhaps that the current > > approach interferes with fio job options like bs_unaligned? > > The main issue I have with that approach is that the core of fio is > generating the IO patterns, and then you are just changing them as you > see fit. This means that the workload definition and the resulting IO > operations are no longer matched up, since they now also depend on what > you are running on. If I take one workload and run it on a zoned drive, > and then run it on a non-zoned drive, I can't compare the results at > all. This is a showstopper. > > There should be no adjusting of the output, rather it should be possible > to write zoned friendly job definitions. It should be possible to run > the same job on a non-zoned drive, and vice versa, and the resulting IO > patterns must be the same. > > Fio already has some notion of zones. Maybe that could be extended to > hard zones, and some control of open zones, and patterns within those > zones? Hello Jens, How about adding a job option that makes it possible to use the zoned block device (ZBD) I/O pattern on non-ZBD devices, requiring that the zone size is set explicitly for non-ZBD devices and maintaining a write pointer not only when performing I/O to a ZBD device but also if a ZBD-style I/O pattern is applied to a non-ZBD disk? This should allow to apply exactly the same workload to a non-ZBD disk as to a ZBD disk. What I derived from the fio source code is as follows (please correct me if I got anything wrong): * The purpose of the zonesize, zonerange and zoneskip job options is to limit the I/O range to a single zone with size "zonesize". The I/O pattern for zoned block devices is different: I/O happens in multiple zones simultaneously. The number of zones to which I/O happens is called the number of open zones. * The purpose of the random_distribution=zoned{_abs} job option is to allow the user to skew a uniform random distribution. This is another workload pattern than the typical pattern for ZBD drives. Thanks, Bart.