Vertica Analytics Platform Version 10.0.x Documentation

Disk Readahead

This topic details how to change Disk Readahead to a supported value. Vertica requires that Disk Readahead be set to at least 2048. The installer reports this issue with the identifier: S0020.

 

  • These commands must be executed with root privileges and assumes the blockdev program is in /sbin.
  • The blockdev program operates on whole devices, and not individual partitions. You cannot set the readahead value to different settings on the same device. If you run blockdev against a partition, for example: /dev/sda1, then the setting is still applied to the entire /dev/sda device. For instance, running /sbin/blockdev --setra 2048 /dev/sda1 also causes /dev/sda2 through /dev/sdaN to use a readahead value of 2048.

RedHat/CentOS and SuSE Based Systems

For each drive in the Vertica system, Vertica recommends that you set the readahead value to at least 2048 for most deployments. The command immediately changes the readahead value for the specified disk. The second line adds the command to /etc/rc.local so that the setting is applied each time the system is booted. Note that some deployments may require a higher value and the setting can be set as high as 8192, under guidance of support.

For systems that do not support /etc/rc.local, use the equivalent startup script that is run after the destination runlevel has been reached. For example SuSE uses /etc/init.d/after.local.

/sbin/blockdev --setra 2048 /dev/sda
echo '/sbin/blockdev --setra 2048 /dev/sda' >> /etc/rc.local

If you are using Red Hat 7.0 or CentOS 7.0 or higher, run the following command as root or sudo:

$ chmod +x /etc/rc.d/rc.local

Ubuntu and Debian Systems

For each drive in the Vertica system, set the readahead value to 2048. Run the command once in your shell, then add the command to /etc/rc.local so that the setting is applied each time the system is booted. Note that on Ubuntu systems, the last line in rc.local must be "exit 0". So you must manually add the following line to etc/rc.local before the last line with exit 0.

For systems that do not support /etc/rc.local, use the equivalent startup script that is run after the destination runlevel has been reached. For example SuSE uses /etc/init.d/after.local.

/sbin/blockdev --setra 2048 /dev/sda