Re: disk i/o test

Den tors 3 mars 2022 kl 14:02 skrev Mihai Popescu <mihscu@gmail.com>:
> I am trying to test some disk i/o speeds and I am stumbled on two questions:
> 1. Does it matter if I set in BIOS Legacy or AHCI for the drive,
> regarding the read/write performance?

Probably yes. AHCI will be better if it works.

> 2. Can you suggest a sane disk I/O benchmark, writing from RAM to disk
> (i.e. cp /dev/null ....)?
>

https://openports.pl/path/benchmarks/fio
To test perf on many small IO (measuring iops basically) run:

fio --name=random-write --rw=write --bs=4k --numjobs=2 --size=1g
--iodepth=16 --runtime=60 --time_based --end_fsync=1

To test large-IO perf:

fio --name=random-write --rw=write --bs=1M --numjobs=1 --size=1g
--iodepth=1 --runtime=60 --time_based --end_fsync=1

Look for the result in the post-run report,
for small IO it can be
write: IOPS=37.8k, BW=148MiB/s (155MB/s)
and for larger writes
write: IOPS=253, BW=253MiB/s (266MB/s)

> I am on snapshots for amd64 and I think i have a really slow writing
> to disk on OpenBSD only.

Might be worth testing mount flags like softdep or (shudder) async if
the data is backed up and not very important.

--
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