I ran into this issue also, for those who use a remote rsyslog server for logs, if you want to avoid using a cron-sed script, edit your /etc/rsyslog.d/UNRAID.log and add this:
$template unraid, "/var/log/unraid.log"
# Filter out specific noisy messages before logging
if ($fromhost-ip == '192.168.UNRAID-IP-HERE' and ($msg contains 'mpt2sas_cm1:') or ($msg contains 'mpt2sas_cm0:')) then stop
# If the message is from the specific host and has not been stopped by the previous rule, log it
if ($fromhost-ip == '192.168.UNRAID-IP-HERE') then -?unraid
& stop
You can add all kinds of "remove if found" filters by using the ($msg contains 'whatever lines you want to remove') - you can use booleans between the parenthesis