Dear John,
I would definitely not go with mdtest. That one can be well optimized by read ahead / sync. Also it is POSIX only.
Note that for overcoming the caching problem, I wrote the md-real-io benchmark that shares many things with mdtest.

I would wait for the community feedback and not ignore that concepts such as ADIOS may not necessarily fit as IOR back ends and rather to with abstract definitions first.


Am 20.11.2016 6:12 nachm. schrieb "John Bent" <>:
To attempt defining the perfect IO benchmark is Quixotic.  Those who dislike IO500 will always dislike IO500 regardless of what the specific benchmark is.  Those who like the idea will accept an imperfect benchmark.

Therefore, I suggest we move forward with the straw person proposal: IOR hard, IOR easy, mdtest hard, mdtest easy.  
  • Average IOR hard and IOR easy.  Average mdtest hard and mdtest easy.  
  • Their product determines the winner.  
  • Don’t report the product since it’s a meaningless unit; report the averages.
  • e.g. The winner of IO500 is TaihuLight with a score of 250 GB/s and 300K IOPs.

Unless a proposal is strictly much better than IOR hard, IOR easy, mdtest hard, mdtest easy, I don’t think we should consider it.  The beauty of IOR hard, IOR easy, mdtest hard, mdtest easy is that they are well-understood, well-accepted benchmarks, that are trivial to download and compile, and whose results are immediately understandable.  Every RFP in the world uses them.  The one problem is they need a pithier name than “IOR hard, IOR easy, mdtest hard, mdtest easy”...

My suggestion is to poll the top 100 of the and ask them this:

"If we were to do an IO500, and our benchmark was IOR hard, IOR easy, mdtest hard, mdtest easy, would you participate?  If not, would you participate with a different benchmark?”

If the bulk of the answers are “yes,” then we just figure out how to organize and administer this thing.
If the bulk of the answers are “no,” then we give up and do something else. 
If the bulk of the answers are “no, yes,” then we need to find a new benchmark.


On Nov 20, 2016, at 7:11 AM, Julian Kunkel <> wrote:

Dear all,
based on our discussion during the BoF at SC, we could focus on the
access pattern(s) of interest first. Later we can define which
benchmarks (such as IOR) could implement these patterns (e.g., how to
call existing benchmarks).

This strategy gives other I/O paradigms the option to create a
benchmark with that pattern that fits their I/O paradigm/architecture.

Here is a draft of one that is probably not too difficult to discuss:
Goal: IOmax: Sustained performance for well-formed I/O

The benchmark shall determine the best sustained I/O behavior without
in-memory caching and I/O variability. A set of real applications that
are highly optimized should be able to show the described access

Use case: A large data structure is distributed across N
threads/processes; a time series of this data structured shall be
stored/retrieved efficiently. (This could be a checkpoint.)

Processing steps:
S0) Each thread allocates and initializes a large consecutive memory
region of size S with a random (but well defined) pattern
S1) Repeat T times: Each process persists/reads its data to/from the
storage. Ech iteration  is protected with a global barrier and the
runtime is measured
S2) Compute the throughput (as IOmax) by dividing the total accessed
data volume (N*S) by the maximum observed runtime for any single
iteration in step S1

R1) The data of each thread and timestep must be stored individually
and cannot be overwritten during a benchmark run
R2) It must be ensured that the time includes all processes needed to
persist all data in volatile memory (for writes) and that prior
startup of reads no data is cached in any volatile memory
R3) A valid result must verify that read returns the expected (random) data
R4) N, T and S can be set arbitrarily. T must be >= 3. The benchmark
shall be repeated several times

Reported metrics:
* IOmax
* Working set size W: N*T*S

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