On 3/3/22 7:59 AM, Mihai Popescu wrote:
Hello,
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?
anywhere between "big difference" and "OH WOW, I CAN'T BELIEVE THEY EVEN
PROVIDE THIS LEGACY OPTION!". Really, you don't want to use "legacy".
Cool thing, you can ignore the BIOS warnings about changing the setting
and being no longer able to boot, OpenBSD handles that well.
2. Can you suggest a sane disk I/O benchmark, writing from RAM to disk
(i.e. cp /dev/null ....)?
really, your best benchmark is your work you need to do. But if you are
looking for repeatable benchmarks, dd'ing FROM /dev/zero or TO /dev/null
is a starting point (use a larger block size than the default -- "bs=1m"
gives you easy to read info info out of "pkill -info dd", but also
consider untaring ports.tar.gz or src.tar.gz.
I am on snapshots for amd64 and I think i have a really slow writing
to disk on OpenBSD only.
You mention "legacy" options in the BIOS, you may be running an old
machine. But also look at softdep and noatime mount options, softdep
is a HUGE performance gain, noatime is a nice little kick with seemingly
zero consequences (it does defeat a standard Unix file system feature,
but I've not come across anything that uses file access time stamps).
Nick.
