Hi, (You just restated your original question verbatim which unfortunately doesn't move the problem forward. I was hoping you were going to point out the exact specific part of the offset modifier concept you were struggling with by using a worked example to show what you did understand and which part you didn't so we could expand on just that. I'll take a stab at explaining things this time but next time try and be specific and briefly demonstrate what bits you did understand if you're asked for clarification :-) I'm just going to quote some text because "offset" in a different context refers to another option: >From https://fio.readthedocs.io/en/latest/fio_doc.html#cmdoption-arg-readwrite : "It is possible to specify the number of I/Os to do before getting a new offset by appending :<nr> to the end of the string given. For a random read, it would look like rw=randread:8 for passing in an offset modifier with a value of 8. If the suffix is used with a sequential I/O pattern, then the <nr> value specified will be added to the generated offset for each I/O turning sequential I/O into sequential I/O with holes. For instance, using rw=write:4k will skip 4k for every write. Also see the rw_sequencer option." So in the above the "offset modifier/suffix" has two different meanings: - With random I/O, the offset suffix is saying "do <nr> I/Os sequentially before randomly* picking another starting point and then doing another <nr> I/Os sequentially" - With sequential I/O the offset suffix refers to the "distance to skip between I/Os" Seen another way, depending on context the offset modifier is controlling the "the offset (distance) chosen from the first allowable position for I/O before doing sequential I/O" or the "offset (distance) from the end of the previous I/O". (Note: I'm skipping over the effect of rw_sequencer in the above to keep this discussion shorter) As to your second question, for many jobs so long as I use the same job options verification should work with an offset modifier. For example: fio --name=gappy_verify --size=512k --filename=/tmp/fio.tmp --rw=write:4k --verify=crc32c wrote every other 4k and then verified it. If you're splitting up your verifies into separate jobs for some reason, you may find the verify_only and do_verify options useful (see https://fio.readthedocs.io/en/latest/fio_doc.html#verification ). Does this help at all? * This is a simplification but it gives you the idea. On Tue, 13 Nov 2018 at 01:20, Mohanraj B <bmohanraj91@xxxxxxxxx> wrote: > > Hi, > > Thanks for the response. > > I have gone through and worked out the example. > Below are my queries: > what is offset? > How to verify the results if used the :<nr> at the end of the string ? > > Thanks and Regards, > Mohan > > On 11/7/18, Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > > Hi, > > > > On Wed, 7 Nov 2018 at 11:31, Mohanraj B <bmohanraj91@xxxxxxxxx> wrote: > >> > >> Hello all, > >> > >> > >> https://fio.readthedocs.io/en/latest/fio_man.html#i-o-type > >> > >> what is offset modifier, some please explain. > >> It is possible to specify the number of I/Os to do before getting a > >> new offset by appending :<nr> to the end of the string given. > > > > I guess you mean mean the rw <nr> parameter in the final paragraph in > > https://fio.readthedocs.io/en/latest/fio_man.html#cmdoption-arg-readwrite > > . Can you say what part of that paragraph and the rw_sequencer section > > you are struggling to understand and did you work through the > > randread:8 and rw=write:4k examples? > > > > -- > > Sitsofe | http://sucs.org/~sits/ > > -- Sitsofe | http://sucs.org/~sits/
