Allow limiting IO operation size (KVM)

[salfers]

ISSUE TYPE

• Improvement Request

COMPONENT NAME

KVM hypervisor

CLOUDSTACK VERSION

4.18 or latest

SUMMARY

The qemu documentation explains why this is important:

When applying IOPS limits all I/O operations are treated equally
regardless of their size. This means that the user can take advantage
of this in order to circumvent the limits and submit one huge I/O
request instead of several smaller ones.

QEMU provides a setting called throttling.iops-size to prevent this
from happening. This setting specifies the size (in bytes) of an I/O
request for accounting purposes. Larger requests will be counted
proportionally to this size.

In libvirt this option is called size_iops_sec inside the <iotune> section (ref).

Other big clouds such as AWS also use this mechanism to fairly allocate IOPS.

STEPS TO REPRODUCE

Checking the CloudStack code shows that this option is currently not supported:

cloudstack/plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtVMDef.java

Lines 1173 to 1207 in 1411da1

	diskBuilder.append("<iotune>\n");
	if ((_bytesReadRate != null) && (_bytesReadRate > 0))
	diskBuilder.append("<read_bytes_sec>" + _bytesReadRate + "</read_bytes_sec>\n");
	if ((_bytesWriteRate != null) && (_bytesWriteRate > 0))
	diskBuilder.append("<write_bytes_sec>" + _bytesWriteRate + "</write_bytes_sec>\n");
	if ((_iopsReadRate != null) && (_iopsReadRate > 0))
	diskBuilder.append("<read_iops_sec>" + _iopsReadRate + "</read_iops_sec>\n");
	if ((_iopsWriteRate != null) && (_iopsWriteRate > 0))
	diskBuilder.append("<write_iops_sec>" + _iopsWriteRate + "</write_iops_sec>\n");
	if (s_qemuVersion >= 2004000) {
	if (_bytesReadRateMax != null && _bytesReadRateMax > 0 ) {
	diskBuilder.append("<read_bytes_sec_max>" + _bytesReadRateMax + "</read_bytes_sec_max>\n");
	}
	if (_bytesWriteRateMax != null && _bytesWriteRateMax > 0) {
	diskBuilder.append("<write_bytes_sec_max>" + _bytesWriteRateMax + "</write_bytes_sec_max>\n");
	}
	if (_iopsReadRateMax != null && _iopsReadRateMax > 0)
	diskBuilder.append("<read_iops_sec_max>" + _iopsReadRateMax + "</read_iops_sec_max>\n");
	if (_iopsWriteRateMax != null && _iopsWriteRateMax > 0)
	diskBuilder.append("<write_iops_sec_max>" + _iopsWriteRateMax + "</write_iops_sec_max>\n");
	}
	if (s_qemuVersion >= 2006000) {
	if (_bytesReadRateMaxLength != null && _bytesReadRateMaxLength > 0) {
	diskBuilder.append("<read_bytes_sec_max_length>" + _bytesReadRateMaxLength + "</read_bytes_sec_max_length>\n");
	}
	if (_bytesWriteRateMaxLength != null && _bytesWriteRateMaxLength > 0) {
	diskBuilder.append("<write_bytes_sec_max_length>" + _bytesWriteRateMaxLength + "</write_bytes_sec_max_length>\n");
	}
	if (_iopsReadRateMaxLength != null && _iopsReadRateMaxLength > 0)
	diskBuilder.append("<read_iops_sec_max_length>" + _iopsReadRateMaxLength + "</read_iops_sec_max_length>\n");
	if (_iopsWriteRateMaxLength != null && _iopsWriteRateMaxLength > 0)
	diskBuilder.append("<write_iops_sec_max_length>" + _iopsWriteRateMaxLength + "</write_iops_sec_max_length>\n");
	}
	diskBuilder.append("</iotune>\n");

[isnuryusuf]

Just wondering, did you manage Limit IOPS when you use Local Storage (as Primary storage) on KVM Hypervisor? i try different QOS Type Hypervisor and Storage both doesn't work

Storage type: Local
QoS type: Hypervisor or Storage
Disk read rate (IOPS): 1000 (Hypervisor type QOS )
Disk write rate (IOPS): 1000 (Hypervisor type QOS )
Min IOPS: 1000 (Storage type QOS )
Max IOPS: 1000 (Storage type QOS )
Provisioning type: Thin