mdraid resync speed after ignition boot (first boot)

[schmitch]

hello, we are building a nvme raid on top of mdraid with flatcar linux and we found out that it takes a really really long time to resync without raising dev.raid.speed_limit_max.

our ignition config is build like: https://www.flatcar.org/docs/latest/setup/storage/raid/
when we manually build the raid:

mdadm --create /dev/md/data_array --level raid10 --name data_array --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1

and call:

sysctl -w dev.raid.speed_limit_max=10000000

it takes like 10 minutes to build the raid, however without it, it takes hours or even more and it's the first boot, is there any way to also specify the dev.raid.speed_limit_max when first boot kicks in?

[pothos]

Did you try setting it through a /etc/sysctl.d/ entry? Otherwise https://www.flatcar.org/docs/latest/setup/customization/other-settings/#tuning-sysctl-parameters has some instructions, too

[pothos]

afterwards

[schmitch]

I have no idea, but this does not look to have any effect, on first boot.

[schmitch]

(in fact it does not work)
so basically I either wait a day or configure mdraid manually or after first boot

[pothos]

So, /etc/sysctl.d/ does not take effect (probably related to the module load time and the linked docs could help) but anyway you would want to assemble the raid in Ignition which is even earlier. The workaround I recommend is not doing in manually but having a systemd unit that does the call to mdadm and sets the sysctl prior to it.

[schmitch]

yeah that's what I figured, still thanks for your input