From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35353) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJljs-0003lK-7E for qemu-devel@nongnu.org; Thu, 04 Oct 2012 09:45:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TJljm-0000yP-7S for qemu-devel@nongnu.org; Thu, 04 Oct 2012 09:45:20 -0400 Received: from cantor2.suse.de ([195.135.220.15]:37751 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJljl-0000wA-VG for qemu-devel@nongnu.org; Thu, 04 Oct 2012 09:45:14 -0400 Message-ID: <506D92E6.7090504@suse.de> Date: Thu, 04 Oct 2012 15:45:10 +0200 From: Hannes Reinecke MIME-Version: 1.0 References: <1347382813-5662-1-git-send-email-Don@CloudSwitch.com> <20120911235020.GC29044@redhat.com> <505081B4.8090301@redhat.com> <87392ngx69.fsf@codemonkey.ws> <50517C05.3080708@redhat.com> In-Reply-To: <50517C05.3080708@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] hw: Add support for new LSI Logic devices. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Kevin Wolf , "Michael S. Tsirkin" , Don Slutz , qemu-devel@nongnu.org, Blue Swirl , Anthony Liguori On 09/13/2012 08:24 AM, Paolo Bonzini wrote: > Il 12/09/2012 15:58, Anthony Liguori ha scritto: >> Why would someone use this verses megasas vs. LSI vs virtio-scsi? > > LSI is dead. Compare it to IDE. > > virtio-scsi has the highest performance, but it is not supported on all > guests. Compare it to virtio-blk. > > This vs. megasas is a good question; both can be compared to AHCI, they > have good performance and have the advantage of compatibility with real > hardware. If this had gone in first, I would probably have rejected > megasas, but this has the advantage of being used in VMware and > VirtualBox. Plus, unlike megasas Don said he'd work on SeaBIOS support= , > so it has further merit. > Ah. Well, I'll be working on SeaBIOS support then, too :-) I just haven't seen the need yet as it boots happily with an=20 external ROM ... However: The main difference here is that the proposed 'lsilogic' controller=20 emulates a SCSI or SAS controller, whereas the megasas emulates a=20 RAID controller. So for the former you have to implement _lot_ of code to make the=20 emulation happy; most of which will be static (just look at the=20 various config pages it'll has to implement) and just adds to the=20 general size of the code without any functional benefit. For megasas the controller itself does an emulation, which maps=20 pretty well to qemu. And you don't have to implement all these=20 transport-specific details. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)