Resolving issues with disk and network input/output performance on a VM

Issue descriptionIssue description

• Services on a VM are running too slow, although the Load Average values and CPU usage levels are small.
• The VM monitoring charts show an increase in the number of deferred disk operations.

SolutionSolution

When the VM's disk subsystem operation exceeds the service limits at any given time, this triggers throttling, resulting in decreased performance of services running on the VM.

Check the VM's internal monitoring data for many deferred disk operations and reaching the technical write limits. You can use the iotop utility to analyze disk subsystem metrics for Linux VMs, or Sysinternals DiskMon for Windows VMs.

In Yandex Cloud, the VM disk performance directly depends on its size:

• If IOWait values reach tens of percent under load for a long period, increase the disk size to the next placement unit threshold.
• If that did not help, change the storage type to SSD. With each 32 GB increment, the number of placement units increases and the disk subsystem performance improves.