OpenBSD softraid monitoring

2021-04-30 - How to properly check a software raid array on OpenBSD
Tag: OpenBSD

Introduction

I have reinstalled my nas recently from gentoo to OpenBSD and was amazed once again at how elegant OpenBSD is. The softraid setup was simple thanks to the wonderful faq. The only thing I changed is that I used a raid5 with 3 disks, but the last line of the faq about the monitoring left the matter as an exercise to the reader.

Softraid monitoring

I had a hard time figuring out how to properly monitor the state of the array without relying on parsing the output of bioctl but at last here it is in all its elegance :

root@nas:~# sysctl hw.sensors.softraid0
hw.sensors.softraid0.drive0=online (sd4), OK

I manually failed one drive (with bioctl -O /dev/sd2a sd4) then rebuilt it (with bioctl -R /dev/sd2a sd4)… then failed two drives in order to have examples of all possible outputs. Here they are if you are interested :

root@nas:~# sysctl hw.sensors.softraid0
hw.sensors.softraid0.drive0=degraded (sd4), WARNING

root@nas:~# sysctl hw.sensors.softraid0
hw.sensors.softraid0.drive0=rebuilding (sd4), WARNING

root@nas:~# sysctl -a |grep -i softraid
hw.sensors.softraid0.drive0=failed (sd4), CRITICAL

Nagios check

I am still using nagios on my personal infrastructure, here is the check I wrote if you are interested :

#!/usr/bin/env perl
###############################################################################
#     \_o<     WARNING : This file is being managed by ansible!      >o_/     #
#     ~~~~                                                           ~~~~     #
###############################################################################

use strict;
use warnings;

##### Arguments processing #####
use Getopt::Long;
my $diskname;
my $usage = "Usage: $0 [OPTIONS]
OPTIONS:
    -d DEVICE_NAME, --device-name=DEVICE_NAME : device name to inspect.";
GetOptions("device-name=s" => \$diskname) or die $usage;
die "You must provide a device-name\n\n$usage" unless $diskname;

##### Softraid Check #####
my %output = (
        "code" => 3,
        "status" => "UNKNOWN",
);
if (`uname` eq "OpenBSD\n") {
        $output{status} = $1 if `sysctl hw.sensors.$diskname.drive0` =~ /=(.*)$/ or do { $!=3; die "UNKNOWN Failed to get sysctl hw.sensors.$diskname.drive0" };
        $output{code} = 0 if ($output{status} =~ /OK$/);
        $output{code} = 1 if ($output{status} =~ /WARNING$/);
        $output{code} = 2 if ($output{status} =~ /CRITICAL$/);
}

print $output{status};
exit $output{code};