Why is the Vertica Host Slow?

Posted June 14, 2018 by Soniya Shah, Information Developer

  • Sluggish response time
  • Server is CPU-bound with a high load and too many processes.
  • The host is possibly in a hung state, unable to make connections, or connections are hanging.
Possible causes:
  • Low available memory
  • Too many concurrent active processes running
  • Server actively using swap space
To troubleshoot, follow this checklist:
Step Task Results
1 Check if the processes or applications are running outside of Vertica. Look at the host uptime or use Linux commands to view the list of processes, memory usage, and CPU activity. $ uptime 09:08:14 up 236 days, 8:58, 13 users, load average: 1.72, 2.09, 2.35Note that the load average values from running uptime represent the last 1, 5, and 15 minutes, respectively. Other commands to view server activity are as follows: top, vmstat, iostat, sar, netstat The top command displays detailed real-time CPU activity, memory usage and details about processes that are currently running. If yes, possibly move those processes to other servers to reduce their impact on the Vertica database host. If no, go to Step 2.
2 Check if memory is low and actively using swap space.
2a. Use the top command to view available memory and swap space usage. Output from the top command appears as below for memory use: Mem: 16333388k total, 4355992k used, 11977396k free, 402180k buffers Swap: 8388604k total, 0k used, 8388604k free, 2365872k cached
2b. You can see the total memory installed (16333388k), and the amount of used memory (4355992k). Swap used should be 0 as in the example. A non-zero value for swap used indicates swap activity and one possible cause for slow host response. For individual processes, the top command returns memory use for each process. This helps you identify any misconfigured applications. If yes,
  • Evaluate the workload running on this host and compare it to other Vertica hosts in the same cluster.
  • Balance the workload and user connections.
  • Check the hardware configuration and memory size.
  • Check if other applications are consuming memory on the Vertica host. Consider moving them to other servers.
2c. Set the vm.swappiness value to 1 on each Vertica host. The default value is 60, because the system easily uses some space on the swap disks. A value of 1 avoids swapping to disk unless absolutely necessary. As root, change the value to 1: $ echo 1 > /proc/sys/vm/swappiness If no, go to Step 3.
2d. To verify the setting: $ cat /proc/sys/vm/swappiness
3 Verify if your security and operation system patches are up to date. Operating system patches can be installed using the yum command.
3a. To download and install latest patches, run: $ yum update
3b. To view certain packages, for example, the latest security updates, run: $ yum updateinfo security If yes, install and update all security and Linux patches.
3c. To install all patches, run: $ yum update If no, go to Step 4.
3d. To install only security patch updates, run: $ yum update --security
4 Review errors and warnings in the vertica.log file located in the catalog directory. Are there errors or other issues that might cause the host to be slow? If yes, check the errors or issues in the Vertica log files and correct them. If no, contact Vertica Technical Support.

Learn More

Learn more about GET hosts in the Vertica Documentation.