Re: Simulating bursts at different rates at irregular intervals?

[Jens Axboe <axboe@kernel.dk>]

On Thu, Jun 27 2013, James Vanns wrote:
> Hi. I'm new to fio and though I've read the HOWTO from the git repo several times now, I'm unsure if it is possible to achieve what I want;
> 
> I can simulate a mix of sequential and random writes for a duration at
> an average rate or throughput of say, 5.4MB/s.  I presume that fio
> will attempt to sustain that rate? My real question is this - is it
> possible in either the same job or a different job in the same file to
> simulate bursts of higher rates? I.e. on average attempt to write at
> nMB/s but at random or irregular intervals during this period attempt
> a 'burst' of 138MB/s for 5 minutes and then return to the 'normal'
> rate. Then again at some other point a burst of 57MB/s for 30minutes
> etc.
> 
> Is this possible? Presently I've found that I cannot do this. Or
> rather, thinking about it, I'd have to specify n jobs for each
> different rate and then perhaps use 'ratecycle' and 'thinktime'? I
> can't see how to skew 'thinktime' randomly though?

That's currently not possible, fio only supports a fixed rate. But if
you have a good idea on how to express your criteria as an option (or
options), then it can surely be added :-)

-- 
Jens Axboe