[PVE-User] Slow speeds when KVM guest is on NFS

Mikhail m at plus-plus.su
Tue Nov 15 15:48:57 CET 2016


Please help me to find why I'm seeing slow speeds when KVM guest is on
NFS storage. I have pretty standard setup, running Proxmox 4.1-1. The
storage server is on NFS connected directly (no switches/hubs, direct
NIC-to-NIC connection) via Gigabit ethernet.

I just launched Debian-8.3 stock ISO installation on the KVM guest
that's disk resides on NFS and I'm seeing some terribly slow file copy
operation speeds on debian install procedure - about 200-600
kilobyte/second according to "bwm-ng" output on storage server. I also
tried direct write from my Proxmox host via NFS using "dd" and results
are showing near 1gbit speeds:

# dd if=/dev/zero of=10G bs=1M count=10000
10000+0 records in
10000+0 records out
10485760000 bytes (10 GB) copied, 115.951 s, 90.4 MB/s

What could be an issue?

On Proxmox host:

# cat /proc/mounts |grep vmnf /mnt/pve/vmnfs nfs
0 0

nfs: vmnfs
	export /mnt/vmnfs
	path /mnt/pve/vmnfs
	content images
	options vers=3
	maxfiles 1

KVM guest config:
# cat /etc/pve/qemu-server/85103.conf
bootdisk: virtio0
cores: 1
ide2: ISOimages:iso/debian-8.3.0-amd64-CD-1.iso,media=cdrom
memory: 2048
name: WEB
net0: virtio=3A:39:66:30:63:32,bridge=vmbr0,tag=85
numa: 0
onboot: 1
ostype: l26
smbios1: uuid=97ea543f-ca64-43ab-9d66-9d1c9cd179b0
sockets: 1
virtio0: vmnfs:85103/vm-85103-disk-1.qcow2,size=50G

Any suggestions where to start looking is greatly appreciated.


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