Storage Node on Compute Resource Uses Too Much CPU

Question

A compute resource seems to be under heavy load. Particularly for the KVM compute resources, the storage-node process uses too many CPU resources.

Environment

OnApp 5.x, 6.x

Answer

Storage-node virtual servers are storage controllers for integrated storage. Their usage of CPU and other resources enables the virtual servers to use the integrated storage to access their disks and take backups. 

Typically, if a storage-node virtual server has a high CPU usage, it means that some virtual servers have heavy disk access. These virtual servers use node(s) that are controlled by the storage-node virtual server and may not be on the same compute resource or even in the same datastore.

The storage node can be telnet into and runs a stripped-down diskless OS. However, simple commands, such as ps and top are available. top can be used to see which disk devices are using resources the most at the moment. It can be checked in the UI and traced back to the virtual server.

It should be easier and safer to check disk usage statistics in the OnApp UI first and determine which virtual servers in the list may load down a particular storage node. Then, appropriate action can be taken.