From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: Feedback and errors Date: Fri, 2 May 2008 15:45:27 +0100 Message-ID: <20080502144527.GH5681@redhat.com> References: <200804282258.08426.nadim@khemir.net> <481AF262.4080305@qumranet.com> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: nadim khemir , kvm-devel@lists.sourceforge.net, qemu-devel@nongnu.org To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <481AF262.4080305@qumranet.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org On Fri, May 02, 2008 at 01:52:18PM +0300, Avi Kivity wrote: > nadim khemir wrote: > > Hi, great work. > > > > While playing with kvm-qemu I noticed a few points that might be of interrest: > > > > 1/ -loadvm and -snapshot don't work together. It works as if -loadvm wasn't > > passed as argument > > > > 2/ two instances of kvm can be passed the same -hda. There is no locking > > whatsoever. This messes up things seriously. That depends entirely on what you are doing with the disk in the guest OS. The disk could be hosting a cluster filesystem. The guest OS could be running on a read-only root FS. The disk could be application raw data storage which can be shared (eg Oracle RAC). And if the disk is backed by a physical volume which is accessible to multiple hosts, locking on the VM's host won't provide any safety against VMs on another host accessing it. > These two are upstream qemu problems. Copying qemu-devel. > > I guess using file locking by default would improve the situation, and > we can add a -drive ...,exclusive=no option for people playing with > cluster filesystems. Turning on file locking by default will break existing apps / deployments using shared disks. IMHO this is a policy decision that should be solved at ahigher level in the management stack where a whole world view is available rather than QEMU which only knows about its own VM & host. Dan. -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone