From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arne Kepp Subject: Poor write- and overall performance Date: Mon, 15 Dec 2008 00:44:17 +0100 Message-ID: <49459A51.7040905@opengeo.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from mail.smallworld.no ([195.1.161.175]:37634 "EHLO mail.smallworld.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348AbYLNXvJ (ORCPT ); Sun, 14 Dec 2008 18:51:09 -0500 Received: from [10.0.0.22] (147.84-48-122.nextgentel.com [84.48.122.147]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.smallworld.no (Postfix) with ESMTPSA id 633DF1A4762 for ; Mon, 15 Dec 2008 00:44:12 +0100 (CET) Sender: kvm-owner@vger.kernel.org List-ID: Hi, I'm testing KVM 80 (prepackaged from lfarkas.org) on CentOS 5.2 (both guest and host) and comparing against Xen 3.3.0. The only modification I've really made is that I've set noatime on both guest and host. The guest is running straight from an LVM volume and is assigned 4 Gb RAM and 4 virtual CPUs. KVM does well reading from disk (300 Mbyte/s according to IOZone, virtually the same as native) and computational tasks like OpenSSL signing. But writing ends up at 30 Mbyte/s (native does 150 Mbyte/s) and kernel compilation times are roughly double that of native. KVM 79 exhibited the same behavior for disk IO, but froze while compiling the kernel. So, short of using the virtio drivers (which I think would require a custom kernel since RHEL 5.2 uses 2.6.18), are there any easy tweaks I should try to make KVM fare better ? The host is quad core Intel with 8 Gb RAM and a SAS RAID 5 configuration. Let me know if you'd like to see the results here. Sincerely, -Arne -- Arne Kepp OpenGeo - http://opengeo.org Expert service straight from the developers