Re: FW: re; fio / test result diffs

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On Thu, 13 Jan 2022 at 00:57, Gibson, Thomas <thomas.gibson@xxxxxxx> wrote:
>
>
> My company builds SDWan network appliances and use SSD's and NVMe's for several key purposes.
>
> In order to qualify upcoming new disks for our systems, we typically run 2 hour test runs using fio, for the following:
>
> seqrd, seqwr, seqrw, seqrd_seqwr
> randrd, randwr, randrw, randrd_randwr, randrd_seqwr
>
> We've noticed that single disk mode tests (ie seqrd, seqwr, etc) show high numbers than their counter parts in multiple disk mode tests (ie seqrd_seqwr).   But we don't understand why.  This may part normal, but we don't understand how testing functions to explain this.  And if it's not normal, what factors might account for it.
>
> I've include a table of test data below.  You'll notice, as an example, the seq read and seq write numbers are much high than the seq read part of seqrd_seqwr and even high than seqrw.
>
> I've also included a package of fio and test execution files in case that helps.
>
> Also prior to each test run, we do a prefill write to the disk and a clearing of the buffer cache, if that helps.
>
>   FIO            SSSTC_CVB-8D120_FW_CZJG801
>   Seq Read                               533MiB/s
>   Seq Write                              317MiB/s
>   Seq Read/Write                   138MiB/s & 138MiB/s   ;  why values are lower here?

An example job from your tarball (included here because it's easier to read)

; Random Read,Sequential Write
[global]
ioengine=libaio
direct=1
iodepth=16
randrepeat=0
bs=256000
time_based
runtime=7200
log_avg_msec=500
[SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-RandRd]
filename=/dev/sde
write_bw_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-randrd
write_iops_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-randrd
write_lat_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-randrd
rw=randread
[SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-SeqWr]
filename=/dev/sde
write_bw_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-seqwr
write_iops_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-seqwr
write_lat_log=SSSTC_CVB-8D120_FW_CZJG801_2ndrun_r640-seqwr
rw=write

What does fio's summary output look like for that job? On Linux, fio
prints disk and CPU utilisation information in its summary when the
job finishes - what does it say? Alternatively take a look at the
"iostat -xzh 1" output while the job is running and see what the disk
utilisation is like.

-- 
Sitsofe




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