fio has settings for buffered and direct

[sdrake]

Hi, newbie here. When running fio I am prompted for settings for both direct and buffered. It seems these settings are redundant. Direct means 'not buffered' and buffered means 'not direct'. What exactly do the results for 'buffered, direct' mean? How about 'not buffered, not direct'? Can someone point me to information that explains why both of these settings are present and specifically what they mean in each of the 4 cases?

[Michael]

Hi, newbie here. When running fio I am prompted for settings for both direct and buffered. It seems these settings are redundant. Direct means 'not buffered' and buffered means 'not direct'. What exactly do the results for 'buffered, direct' mean? How about 'not buffered, not direct'? Can someone point me to information that explains why both of these settings are present and specifically what they mean in each of the 4 cases?

It's mostly a legacy remnant at this point and rather redundant for every modern Linux file-system I am aware of... Will try to remember to just drop the next time I touch that test profile. Many years ago IIRC there were some configurations where it made a difference.

[sdrake]

Ok, for SLES15 SP5 testing on xfs filesystems, results for 'buffered, not direct' are the same as 'buffered, direct'....and.... results for 'not buffered, not direct' are the same as 'not buffered, direct". So it makes sense to just test with buffered and not buffered, leaving direct=false.

[sdrake]

Testing again today....fio is now fio-2.1.0 and get error trying to start, error assigning NUMJOBS=/uPD. It seems that the Buffered Option has been removed which is good, but the variable numbers in fio.run were not changed to match. I got it to work by changing $7 to $6 and $6 to $5