Quote Originally Posted by Anvil View Post
...A file is written either using 1 io or using 3 ios, max blocksize/transfersize is 4MB, it needs some more explaining so here we go.

50% of the files are created using one write operation with a max blocksize of 128KB, as for the other half
each file consits of exactly 3 WriteFile operations, each IO can be up to 4MB in size, so it is sort of random. (even though the data is written sequentially)...
Thanks for the explanation!

Looks like the file I/O operation activity as described basically coincides with the random/sequential metrics observed by hIOmon further down at the "physical disk" level within the Windows OS I/O stack.

I think that it's important to distinguish between I/O operations performed "logically" within a file and the I/O operations subsequently performed at the "physical device".

As you mentioned, writing to a file can consist of three successive "sequential" write file I/O operations (which together comprise the entire length/size of the file).

However, each of these three write file I/O operations can actually be to non-contiguous locations upon the device. And so, hIOmon observes the three write I/O operations to the device as "random" write I/O operations.

Filesystem (re)allocation of clusters can also be a factor - but I don't want to go off topic here.

In any case, many thanks to you, Ao1, and One_Hertz for undertaking this exercise!