Enabling or disabling defrag

You can modify the defrag utility to meet Vertica configuration requirements, or to optimize your system performance by workload.

On all Red Hat/CentOS systems, you must disable the defrag utility to meet Vertica configuration requirements.

Note

The steps to disable defrag on Red Hat 6/CentOS 6 systems differ from those used to disable defrag on Red Hat 7/CentOS 7 and Red Hat 8/CentOS 8.

For SUSE 15.1, Vertica recommends that you enable defrag for optimized performance.

Recommended settings by workload for red hat 8/CentOS 8 and SUSE 15.1

Vertica recommends defrag settings to optimize performance by workload. The following table contains recommendations for systems that primarily run concurrent queries (such as short-running dashboard queries), or sequential SELECT or load (COPY) queries:

Operating System	Concurrent	Sequential
Red Hat 8.0/CentOS 8.0	Disable	Disable
SUSE 15.1	Enable	Enable

See Enabling or disabling transparent hugepages for additional settings that optimize your system performance by workload.

Disabling defrag on red hat 6/CentOS 6 systems

Determine if defrag is enabled by running the following command:
```
cat /sys/kernel/mm/redhat_transparent_hugepage/defrag
[always] madvise never
```
The setting returned in brackets is your current setting. If you are not using madvise or never as your defrag setting, then you must disable defrag.

Edit /etc/rc.local, and add the following script:

if test -f /sys/kernel/mm/redhat_transparent_hugepage/enabled; then
    echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag
fi

You must reboot your system for the setting to take effect, or run the following echo line to proceed with the install without rebooting:

# echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag

Disabling defrag on red hat 7/CentOS 7, red hat 8/CentOS 8, and SUSE 15.1

Determine if defrag is enabled by running the following command:
```
cat /sys/kernel/mm/transparent_hugepage/defrag
[always] madvise never
```
The setting returned in brackets is your current setting. If you are not using madvise or never as your defrag setting, then you must disable defrag.

Edit /etc/rc.local, and add the following script:

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
    echo never > /sys/kernel/mm/transparent_hugepage/defrag
fi

You must reboot your system for the setting to take effect, or run the following echo line to proceed with the install without rebooting:

# echo never > /sys/kernel/mm/transparent_hugepage/defrag

If you are using Red Hat 7.0/CentOS 7.0 or Red Hat 8.0/CentOS 8.0, run the following command as root or sudo:
```
$ chmod +x /etc/rc.d/rc.local
```

Enabling defrag on red hat 7/8, CentOS 7/8, and SUSE 15.1

Determine if defrag is enabled by running the following command:
```
cat /sys/kernel/mm/transparent_hugepage/defrag
[never] madvise never
```
The setting returned in brackets is your current setting. If you are not using madvise or always as your defrag setting, then you must enable defrag.

Edit /etc/rc.local, and add the following script:

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
    echo always > /sys/kernel/mm/transparent_hugepage/defrag
fi

You must reboot your system for the setting to take effect, or run the following echo line to proceed with the install without rebooting:

# echo always > /sys/kernel/mm/transparent_hugepage/defrag

If you are using Red Hat 7.0/CentOS 7.0 or Red Hat 8.0/CentOS 8.0, run the following command as root or sudo:
```
$ chmod +x /etc/rc.d/rc.local
```