Ubuntu – What could cause very slow (3 MB/s) disk access on a Ubuntu guest running under Hyper-V

hyper-vperformanceUbuntu

I have a Ubuntu 11.10 x64 guest running under Hyper-V on Windows Server 2008 R2 SP1, configured according to these directions, including installation of the hyper-v modules. Network speed is fine (500 MB/s, measured with iperf), but disk access is laughable (3 MB/s, measured with dd).

What could possibly be causing this issue?

My other Ubuntu VMs have the same problem, my Windows VMs do not have this problem.

Best Answer

I'm not sure if this has been fixed, but at one point you had to enable the Hyper-V modules in Ubuntu 10.04/2.6.x kernel (/etc/initramfs-tools/modules):

hv_vmbus

hv_storvsc

hv_blkvsc

hv_netvsc

Related Solutions

Hyper-V limit disk usage of a VM

No. You will either need to change your storage. Whether it is a faster disk, or separate the .vhd to another spindle entirely, or make it a physical server.

Ubuntu – Incredibly high latency for Ubuntu guest on Hyper-V

Since it's a new system, it may have needed to download and install quite a few updated packages. If the slowness is still present, try doing something like

ps -ef|grep apt

on the virtual machine to see if there's an apt-related process running. If the slowness suddenly resolved itself, it's worth checking /var/log/dpkg.log to see if a bunch of packages were installed, causing the slowness.

Best Answer

Related Solutions

Hyper-V limit disk usage of a VM

Ubuntu – Incredibly high latency for Ubuntu guest on Hyper-V

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