As I stated previously, the session I learned the most from at Hadoop Summit was about performance tuning the OS to ensure the cluster is getting the most from the infrastructure (slides can be found here). In order to do so, I had to modify the Chef recipes inside of the BDE management server to have the updates installed on all new clusters.

• Disable swampiness, increase the proc and file limits in /opt/serengeti/cookbooks/cookbooks/hadoop_cluster/recipes/dedicated_server_tuning.rb

   3 ulimit_hard_nofile = 32768
   4 ulimit_soft_nofile = 32768
   5 ulimit_hard_nproc = 32768
   6 ulimit_soft_nproc = 32768
   7 vm_swappiness = 0
   8 redhat_transparent_hugepage = "never"
   9 vm_swappiness_line = "vm.swappiness = 0"
  10
  11 def set_proc_sys_limit desc, proc_path, limit
  12   bash desc do
  13     not_if{ File.exists?(proc_path) && (File.read(proc_path).chomp.strip == limit.to_s) }
  14     code  "echo #{limit} > #{proc_path}"
  15   end
  16 end
  17
  18 def set_swap_sys_limit desc, file_path, limit
  19   bash desc do
  20     not_if{ File.exists?(file_path) && (File.read(file_path).chomp.strip == limit.to_s) }
  21     code  "echo #{limit} > #{file_path}"
  22   end
  23 end
  24
  25 set_proc_sys_limit "VM overcommit ratio", '/proc/sys/vm/overcommit_memory', overcommit_memory
  26 set_proc_sys_limit "VM overcommit memory", '/proc/sys/vm/overcommit_ratio',  overcommit_ratio
  27 set_proc_sys_limit "VM swappiness", '/proc/sys/vm/swappiness', vm_swappiness
  28 set_proc_sys_limit "Redhat transparent hugepage defag", '/sys/kernel/mm/redhat_transparent_hugepage/defrag', redhat_transparent_hugepage
  29 set_proc_sys_limit "Redhat transparent hugepage enable", '/sys/kernel/mm/redhat_transparent_hugepage/enabled', redhat_transparent_hugepage
  30
  31 set_swap_sys_limit "SYSCTL swappiness setting", '/etc/sysctl.conf', vm_swappiness_line

• Remove root reserved space from the filesystems in /opt/serengeti/cookbooks/cookbooks/hadoop_common/libraries/default.rb

335 function format_disk_internal()
336 {
337   kernel=`uname -r | cut -d'-' -f1`
338   first=`echo $kernel | cut -d '.' -f1`
339   second=`echo $kernel | cut -d '.' -f2`
340   third=`echo $kernel | cut -d '.' -f3`
341   num=$[ $first*10000 + $second*100 + $third ]
342
343   # we cannot use [[ "$kernel" < "2.6.28" ]] here becase linux kernel
344   # has versions like "2.6.5"
345   if [ $num -lt 20628 ];
346   then
347     mkfs -t ext3 -b 4096 -m 0 $1;
348   else
349     mkfs -t ext4 -b 4096 -m 0 $1;
350   fi;
351 }

# knife cookbook upload -a