System configuration
Do the following configuration steps on each of the nodes in the cluster.
ntp
If your instance does not have public Internet access, make sure the ntp package is installed:
$ sudo yum install -y ntp
Note
As of CentOS 8, ntp is no longer available and has been replaced by chrony. To install, run:
$ sudo yum install -y chrony
ulimits
In Linux, ulimit is used to limit and control the usage of system resources (threads, files, and network connections) on a per-process or per-user basis.
Checking ulimits
Run the following command to check the ulimit settings.
$ ulimit -a
The following settings are recommended when running YugabyteDB.
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 119934
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1048576
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 12000
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
Setting system-wide ulimits
You can change values by substituting the -n option for any possible value in the output of ulimit -a. Issue a command in the following form to change a ulimit setting.
$ ulimit -n <value>
-f (file size): unlimited
-t (cpu time): unlimited
-v (virtual memory): unlimited [1]
-l (locked-in-memory size): unlimited
-n (open files): 64000
-m (memory size): unlimited [1] [2]
-u (processes/threads): 64000
Note
- After changing a ulimit setting, the YB-Master and YB-TServer servers must be restarted in order for the new settings to take effect. Check the
/proc/<process pid>file to see the current settings. - Changes made using ulimit may revert following a system restart depending on the system configuration.
These settings should be applied permanently by adding the following in /etc/security/limits.conf.
* - core unlimited
* - data unlimited
* - fsize unlimited
* - sigpending 119934
* - memlock 64
* - rss unlimited
* - nofile 1048576
* - msgqueue 819200
* - stack 8192
* - cpu unlimited
* - nproc 12000
* - locks unlimited
On CentOS, /etc/security/limits.d/20-nproc.conf must also be configured to match.
* soft nproc 12000
Note
If you're using systemd to start the processes, and the ulimits are not propagated, you
must add them also in the Service section in the configuration file.
[Unit]
.....
[Service]
.....
ulimits options here
[Install]
.....
The mappings of ulimit options with values are:
| Data type | ulimit equivalent | Value |
|---|---|---|
| Directive | ulimit equivalent | Value |
| LimitCPU= | ulimit -t | infinity |
| LimitFSIZE= | ulimit -f | infinity |
| LimitDATA= | ulimit -d | infinity |
| LimitSTACK= | ulimit -s | 8192 |
| LimitCORE= | ulimit -c | infinity |
| LimitRSS= | ulimit -m | infinity |
| LimitNOFILE= | ulimit -n | 1048576 |
| LimitAS= | ulimit -v | infinity |
| LimitNPROC= | ulimit -u | 12000 |
| LimitMEMLOCK= | ulimit -l | 64 |
| LimitLOCKS= | ulimit -x | infinity |
| LimitSIGPENDING= | ulimit -i | 119934 |
| LimitMSGQUEUE= | ulimit -q | 819200 |
| LimitNICE= | ulimit -e | 0 |
| LimitRTPRIO= | ulimit -r | 0 |
If a ulimit is set to unlimited, set it to infinity in the systemd config.
Note
After changing aulimit setting in /etc/security/limits.conf, you will need to log out and back in. To update system processes, you may need to restart.
Note
If you're using a desktop-distribution, such as ubuntu-desktop, the settings above may not suffice.
The OS needs additional steps to change ulimit for gui login. In the case of ubuntu-desktop:
In /etc/systemd/user.conf and /etc/systemd/system.conf, add at the end of file DefaultLimitNOFILE=64000.
Something similar may be needed for other distributions.
transparent hugepages
Transparent hugepages should be enabled for optimal performance. By default, they are enabled.
You can check with the following command:
$ cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never
It is generally not necessary to adjust the kernel command line if the above value is correct.
However, if the value is set to "madvise" or "never", you should modify your kernel command line to set transparent hugepages to "always".
You should consult your operating system docs to determine the best way to modify a kernel command line argument for your operating system, but on RHEL or Centos 7 or 8, using grub2, the following steps are one solution:
Append "transparent_hugepage=always" to GRUB_CMDLINE_LINUX in /etc/default/grub
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap ... transparent_hugepage=always"
Rebuild /boot/grub2/grub.cfg using grub2-mkconfig.
Please ensure to take a backup of the existing /boot/grub2/grub.cfg before rebuilding.
On BIOS-based machines:
# grub2-mkconfig -o /boot/grub2/grub.cfg
On UEFI-based machines:
# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
Reboot the system.