Linux OS Tuning/Optimizations
High i/o wait tuning for File Servers
Under “Server”→“General” tab, change “Priority” configuration to “-19”. Process priority can be set from -19 to 20, -19 is the highest, 20 is the lowest.
Change to 'deadline' I/O scheduler
- From command line (change the device 'sda' to appropriate device):
echo “deadline” > /sys/block/sda/queue/scheduler
- kernel parameter, change /boot/grub/menu.lst, add kernel parameter
elevator=deadline
Change VM parameters
There are two variables which control the behaviour of VM flushing and allocation and affect network and disk performance
- vm.dirty_background_ratio
- vm.dirty_ratio
To set these values from command line
echo 20 > /proc/sys/vm/dirty_background_ratio echo 60 > /proc/sys/vm/dirty_ratio
to make it permanent, edit /etc/sysctl.conf:
vm.dirty_background_ratio = 20 vm.dirty_ratio = 60
Increase readahead
To get current readahead value:
$ blockdev --getra /dev/sda 256
To increase it to a higher value like 16K:
$ blockdev --setra 16384 /dev/sda
Disable updating access time stamp for file system
Edit /etc/fstab, remove “atime” attribute if there is, add “noatime” attribute. The noatime change can significantly improve your server's file i/o performance.
#sample /etc/fstab line before change LABEL=/ / ext3 defaults 1 1 #sample /etc/fstab line after noatime change LABEL=/ / ext3 defaults ,noatime 1 1
Kernel Network Tuning
Add the follwing to /etc/sysctl.conf
#increase local ports net.ipv4.ip_local_port_range = 1024 65535 #reduce the number of time_wait connections #these 3 lines can reduce your time_wait count by several hundred percent. #however you should not use the following lines in a NATed configuration. net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_tw_recycle = 1 net.ipv4.tcp_fin_timeout = 30
Then call sysctl to make them active
sysctl -p