[PVE-User] Very slow server (RAW IDE discs and KVM)

Holger Hampel | RA Consulting h.hampel at rac.de
Wed Aug 10 10:35:37 CEST 2011

Hallo Erik,

If you have real I/O while the machine is doing nothing useful it might be paging.

Look at the PAG line of atop - the number should be very small. If not the host is paging. You have to low memory or oversized the memory of your windows guest.

If the host paging ist low, there may be paging in the guest (for the host this is normal disk i/o). Look in the windows task manager for memory usage.


-----Ursprüngliche Nachricht-----
Von: pve-user-bounces at pve.proxmox.com [mailto:pve-user-bounces at pve.proxmox.com] Im Auftrag von Erik van Ast
Gesendet: Mittwoch, 10. August 2011 09:26
An: pve-user at pve.proxmox.com
Betreff: Re: [PVE-User] Very slow server (RAW IDE discs and KVM)

Hi all,

Server is still slow, but with the help of some of you I have tested
some more things which might tell the experts the reason for this server
being so slow.

First of all I installed atop on the Proxmox server so I could see how
my discs, CPU and RAM were doing.
Firstly I tried to change both discs from IDE to VIRTIO but that didn't
make much difference and also changing the network driver to VIRTIO
didn't change much. I tried shutting down both virtual machines on this
Proxmox and restarting the Proxmox, but that also didn't do much good
for the speed of this machine. When turning on only this (2003) machine,
the speed of that machine is very slow, but when only turning on the
other (2008) machine, everything seems fine, so I think it must have
something to do with this machine alone.
One thing that I see when using atop is that the DSK value tells me the
disc is busy for 95-99% when the 2003 virtual server is busy and when it
has been turned off the DSK value is somewhere between 5-10%. I also
created a new machine, but when installing this new machine, the DSK
value also raised to 95-99% so something must be wrong....

Here the output of : pveversion -v

pve-manager: 1.8-18 (pve-manager/1.8/6070)
running kernel: 2.6.32-4-pve
proxmox-ve-2.6.32: 1.8-33
pve-kernel-2.6.32-4-pve: 2.6.32-33
pve-kernel-2.6.18-2-pve: 2.6.18-5
qemu-server: 1.1-30
pve-firmware: 1.0-11
libpve-storage-perl: 1.0-17
vncterm: 0.9-2
vzctl: 3.0.28-1pve1
vzdump: 1.2-14
vzprocps: 2.0.11-2
vzquota: 3.0.11-1
pve-qemu-kvm: 0.14.1-1
ksm-control-daemon: 1.0-6

Who knows what to do next?

Kind regards,


Message: 1
Date: Mon, 8 Aug 2011 12:04:44 +0200
From: "Erik van Ast" <Erik.van.Ast at suzohapp.nl>
To: <pve-user at pve.proxmox.com>
Subject: Re: [PVE-User] Very slow server (RAW IDE discs and KVM)
<80A72F1B1CFF80409D8E422437CEDC9A02537C71 at srv03-suzo-03.Suzo.int>
Content-Type: text/plain;	charset="us-ascii"

Hi all,

Sorry for the previous 2 messages I've send this morning. I forgot the
change the subject and the rest of the message....

@Fabian and @CoolCold thank you for your reply.
I have connected with putty (SSH) and ran #top.
I see 4 CPU lines (CPU0-CPU4) and the max I have seen now during 5
minutes of watching it is 15%, but most of the times, it's 1 Cpu doing
4% and 1 doing 2%, so I presume that's not the problem?

I also edited the .conf file located in /etc/qemu-server and I have
tried both " ide0: local:108/vm-108-disk-1.raw,cache=writethrough" and "
ide0: local:108/vm-108-disk-1.raw,cache=none" but with both configs I
didn't see any major improvements. The virtual server has been installed
with 2 virtual discs, 1 of 40GB and the second with 200GB.
The machine is especially slow when copying large data over, than the
speed drops to about 30-70 Kbyte/sec instead of at least 20 Mbyte/sec...

Anyone seen this before? Help is greatly appreciated...

Kind regard,
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