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VIRTIO Sequential Write IOPS limits not working
Root Problem:
IOPS limit does not work for VIRTIO devices if the disk workload is a sequential write.
To confirm:
IDE disk devices - the IOPS limit works fine. Disk transfer speed limit works fine.
VIRTIO disk devices - the IOPS limit works fine for random IO (write/read) and sequential read, but not for sequential write. Disk transfer speed limits work fine.
Tested on Windows 7,10 and 2k12 (Fedora drivers used and here is the twist):
virtio-win-0.1.96 (stable) or older won't limit write IO if workload is sequential.
virtio-win-0.1.105 (latest) or newer will limit but I have had two test machines crash when under high workload using IOPS limit.
For Linux:
The issue is also apparent, tested on Ubuntu 14.04
On the hypervisor (using KVM) machine I have tried with Qemu 2.1.2 (3.16.0-4-amd64 - Debian 8) and Qemu 2.3.0 (3.19.8-1-pve - Proxmox 3.4 and 4) using multiple machines but all are 64bit intel.
Even though the latest VIRTIO guest drivers fix the problem, the guest drivers shouldn't be able to ignore the limits the host puts in place or am I missing something??
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