Optimize Database Server Performance for Peak Efficiency
Now, to ensure your systems are functioning at peak efficiency, you should run the database server optimally by following the procedures outlined below.
– kernel.shmmax=268435456 for 32-bit
– kernel.shmmax=1073741824 for 64-bit
– kernel.msgmni=1024- fs.file-max=8192
– kernel.sem=”250 32000 32 1024″
Shared Memory
Shared Memory
To view current settings, run the command:
# more /proc/sys/kernel/shmmax
To set it to a new value for this running session, which takes effect immediately, run the command:
# echo 268435456 > /proc/sys/kernel/shmmax
To set it to a new value permanently (so it survives reboots), modify the sysctl.conf file:
…
kernel.shmmax = 268435456
Semaphores
To view current settings, run the command:
# more /proc/sys/kernel/sem
250 32000 32 1024
To set it to a new value for this running session, which takes effect immediately, run the command:
# echo 500 512000 64 2048 > /proc/sys/kernel/sem
Parameters meaning:
SEMMSL – semaphores per ID
SEMMNS – (SEMMNI*SEMMSL) max semaphores in system
SEMOPM – max operations per semop call
SEMMNI – max semaphore identifiers
ulimits
To view current settings, run the command:
# ulimit -a
To set it to a new value for this running session, which takes effect immediately, run the command:
# ulimit -n 8800
# ulimit -n -1 // for unlimited; recommended if server isn’t shared
Alternatively, if you want the changes to survive reboot, do the following:
– Exit all shell sessions for the user you want to change limits on.
– As root, edit the file /etc/security/limits.conf and add these two lines toward the end:
user1 soft nofile 16000
user1 hard nofile 20000
** The two lines above change the max number of file handles – nofile – to new settings.
– Save the file.
– Login as the user1 again. The new changes will be in effect.
Message queues
To view current settings, run the command:
# more /proc/sys/kernel/msgmni
# more /proc/sys/kernel/msgmax
To set it to a new value for this running session, which takes effect immediately, run the command:
# echo 2048 > /proc/sys/kernel/msgmni
# echo 64000 > /proc/sys/kernel/msgmax
Network
Moreover, Gigabit-based network interfaces include several performance-related parameters within their device drivers, such as CPU affinity. In addition, the TCP protocol can be fine-tuned to improve network throughput, especially for connection-intensive or high-demand applications.
Tune TCP
To view current TCP settings, run the command:
# sysctl net.ipv4.tcp_keepalive_time
net.ipv4.tcp_keepalive_time = 7200 // 2 hours
where net.ipv4.tcp_keepalive_time is a TCP tuning parameter.
To set a TCP parameter to a value, run the command:
# sysctl -w net.ipv4.tcp_keepalive_time=1800
A list of recommended TCP parameters, values, and their meanings:
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Disk I/O
Choose the Right File System
Use ‘ext3’ file system in Linux.
– It is an enhanced version of ext2
– With journaling capability – high level of data integrity (in event of unclean shutdown)
– It does not need to check disks on unclean shutdown and reboot (time-consuming)
– Faster write – ext3 journaling optimizes hard drive head motion
# mke2fs -j -b 2048 -i 4096 /dev/sda
mke2fs 1.32 (09-Nov-2002)
/dev/sda is the entire device, not just one partition!
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
13107200 inodes, 26214400 blocks
1310720 blocks (5.00%) reserved for the super user
First data block=0
1600 block groups
16384 blocks per group, 16384 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816, 1327104,
2048000, 3981312, 5619712, 10240000, 11943936
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
Use ‘noatime’ File System Mount Option
Use ‘noatime’ option in the file system boot-up configuration file ‘fstab’. Edit the fstab file under /etc. This option works best if external storage is used, for example, SAN:
# more /etc/fstab
LABEL=/ / ext3 defaults 1 1
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sdc2 swap swap defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner,kudzu 0 0
/dev/sda /database ext3 defaults,noatime 1 2
/dev/sdb /logs ext3 defaults,noatime 1 2
/dev/sdc /multimediafiles ext3 defaults,noatime 1 2
Tune the Elevator Algorithm in Linux Kernel for Disk I/O
After selecting the appropriate file system, it is important to note that several kernel and mounting options can significantly influence overall performance. For example, one crucial kernel parameter is the elevator algorithm, which manages how disk I/O requests are scheduled. Moreover, tuning the elevator algorithm allows the system to balance the need for low latency with the goal of efficiently batching read and write operations to the disk.
Consequently, administrators can optimize file system performance by adjusting the elevator algorithm using the following command:
# elvtune -r 1024 -w 2048 /dev/sda
/dev/sda elevator ID 2
read_latency: 1024
write_latency: 2048
max_bomb_segments: 6
The parameters are: read latency (-r), write latency (-w), and the device affected.
Red Hat recommends using a read latency half the size of the write latency (as shown).
As usual, to make this setting permanent, add the ‘elvtune’ command to the
/etc/rc.d/rc.local script.
Others
Disable Unnecessary Daemons (They Take up Memory and CPU)
In addition, most servers run several daemons (background services) that may not be necessary for normal operation. By identifying and disabling these unnecessary daemons, administrators can free up system memory, reduce startup time, and minimize CPU load. As a result, the system operates more efficiently and with improved overall performance.
Moreover, an added benefit of disabling unused daemons is enhanced server security—since fewer active processes mean fewer potential vulnerabilities or exploitable services.
Some example Linux daemons running by default (and should be disabled). Use command:
#/sbin/chkconfig –levels 2345 sendmail off
#/sbin/chkconfig sendmail off
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Shutdown GUI
Typically, there is no need to install a Graphical User Interface (GUI) on a Linux server, as all essential administrative tasks can be efficiently performed using the command line, by redirecting the X display, or through a web-based management interface.
Therefore, to improve system performance and resource efficiency, it’s recommended to disable the GUI by setting the default runlevel to 3 (multi-user, non-graphical mode). You can do this by modifying the 'inittab' file as shown below:
To set the initial runlevel (3 instead of 5) of a machine at boot,
modify the /etc/inittab file as shown:
modify the /etc/inittab file as shown:
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