From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piavlo Subject: What io scheduler to use inside guest VM? Date: Sat, 21 Mar 2009 22:53:33 +0200 Message-ID: <49C553CD.1070800@cs.bgu.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from smtp2.bgu.ac.il ([132.72.126.39]:48251 "EHLO smtp2.bgu.ac.il" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752284AbZCUUxh (ORCPT ); Sat, 21 Mar 2009 16:53:37 -0400 Received: from smtp2.bgu.ac.il (localhost.localdomain [127.0.0.1]) by postfix.imss70 (Postfix) with ESMTP id 2D535AB875 for ; Sat, 21 Mar 2009 22:53:31 +0200 (IST) Received: from zopa.no-ip.org (unknown [194.90.167.171]) by smtp2.bgu.ac.il (Postfix) with ESMTP id D22C4AB872 for ; Sat, 21 Mar 2009 22:53:30 +0200 (IST) Sender: kvm-owner@vger.kernel.org List-ID: Hi, I use LVM volumes as guest VM disk. I'm wondering if setting setting the io scheduler inside linux gest has any effect (with virtio disk driver and with emulated scsi or ide driver) And if it has affect what's better choice ? My thoughts is that if changing the scheduler inside guest has affect - then it's probably best to use noop scheduler inside the guest and let the hypervisor linux decide according to it's scheduler. So what I don't understand is if there are two levels of io scheduling , one inside the guest (the redundant one and setting it to noop will minimize it's affect) and other inside the hypervisor linux?(or just one level in the hypervisor) Probably with virtio driver tthere is no io scheduling inside the guest, but is it so with emulated drivers too? And also is there any difference in io scheduling if I use image file instead of LVM? Thanks a lot Alex