Save large amount of data in Redis

1. make sure the Redis work directory is in a partition own free space larger than memory

2. to avoid BGSAVE fail with a fork() error even with a lot of availbe memory
   http://stackoverflow.com/questions/11752544/redis-bgsave-failed-because-fork-cannot-allocate-memory

   • run echo 1 > /proc/sys/vm/overcommit_memory as temporary solution.
   • add vm.overcommit_memory=1 to /etc/sysctl.conf and reboot as a long term solution

3. keep writing when BGSAVE error
   in /etc/redis.conf, add or modify stop-writes-on-bgsave-error no

4. disable Transparent Huge Pages(THP)
   This will create latency and memory usage issue with redis.
   Run the following command, and add it to /etc/rc.local to retain the setting after reboot

   sudo echo never > /sys/kernel/mm/transparent_hugepage/enabled

5. enlarge TCP backlog setting
   Run the following command, and add it to /etc/rc.local to retain the setting after reboot

   sysctl -w net.core.somaxconn=65535