IOPS (Input/Output Operations Per Second)¶

Отличная подборка для понимания показателя IOPS:
http://en.wikipedia.org/wiki/IOPS

Утилита тестирования (gentoo):
sys-block/fio-2.0.7:0::ekb-info

IOPS в QEMU-KVM
http://wiki.qemu.org/Features/VirtioIoeventfd

DiskIOLimits в QEMU-KVM еще не готов:
http://wiki.qemu.org/Features/DiskIOLimits

Background

When several instances of QEMU are running they can interfere with system performance through excessive disk I/O. Sometimes it is desirable to limit disk I/O in order to keep QEMU from affecting other applications or instances.

The availability of disk I/O throttling depends on the underlying storage (image file, LVM, NFS, Ceph). On Linux the cgroups blkio-controller supports I/O throttling on block devices but is a relatively recent feature. More importantly, there is no single mechanism for disk I/O throttling across all underlying storage types and for some types there is no way to throttle at all.

The disk I/O limits feature introduces QEMU block layer I/O limits together with command-line and QMP interfaces for configuring limits. This allows I/O limits to be imposed across all underlying storage types using a single interface.