Set IO Scheduler

[slashterix]

# Set the IO Scheduler
node['block_device'].select { |device, info| device =~ /^.d.$/ && info['size'].to_i > 0 }.each do |device, info|
  execute "scheduler-#{device}" do
    command "echo 'deadline' > /sys/block/#{device}/queue/scheduler"
    not_if "grep -F '[deadline]' /sys/block/#{device}/queue/scheduler"
  end
end

Possibly related to #642

I set my compute nodes to deadline and had a 40% reduction in load average. The instances also became much more responsive.