This is a multi-part message in MIME format. ------=_NextPartTM-000-e5c11ff1-4bb3-4471-9f08-8adebae2667b Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hello,=0A= =0A= coming from the "low cost NFS storage thread" I will open a new one=0A= about a topic that might be interesting for others too.=0A= =0A= We see a quite a heavy latency penalty using KVM VirtIO disks in comparison= =0A= to ESX. Doing one I/O onto disk inside a VM usually adds 370us of overhead = in=0A= the virtualisation layer. This has been tested with VirtIO-SCSI and windows= =0A= guest (2K3). More here (still now answer yet):=0A= =0A= http://lists.nongnu.org/archive/html/qemu-discuss/2013-12/msg00028.html=0A= =0A= A comparison for small sequential 1K I/Os on a NFS datastore in our setup g= ives:=0A= =0A= - access NFS inside the hypervisor - 12.000 I/Os per second - or 83us laten= cy =0A= - access DISK inside ESX VM that resides on NFS - 8000 I/Os per second - or= 125us latency=0A= - access DISK inside OVirt VM that resides on NFS - 2200 I/Os per second - = or 450us latency=0A= =0A= Even the official document at http://www.linux-kvm.org/page/Virtio/Block/La= tency=0A= suggest that the several mechanisms (iothread/vcpu) at least have a overhea= d=0A= of more than 200us=0A= =0A= Has anyone experienced something simlar. If these latency are normal it wou= ld =0A= make no sense to think about SSDs inside a central storage (be it ISCSI or = NFS =0A= or whatever).=0A= =0A= Markus=0A= =0A= ------=_NextPartTM-000-e5c11ff1-4bb3-4471-9f08-8adebae2667b Content-Type: text/plain; name="InterScan_Disclaimer.txt" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="InterScan_Disclaimer.txt" **************************************************************************** Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet. Über das Internet versandte E-Mails können unter fremden Namen erstellt oder manipuliert werden. Deshalb ist diese als E-Mail verschickte Nachricht keine rechtsverbindliche Willenserklärung. Collogia Unternehmensberatung AG Ubierring 11 D-50678 Köln Vorstand: Kadir Akin Dr. Michael Höhnerbach Vorsitzender des Aufsichtsrates: Hans Kristian Langva Registergericht: Amtsgericht Köln Registernummer: HRB 52 497 This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. e-mails sent over the internet may have been written under a wrong name or been manipulated. That is why this message sent as an e-mail is not a legally binding declaration of intention. Collogia Unternehmensberatung AG Ubierring 11 D-50678 Köln executive board: Kadir Akin Dr. Michael Höhnerbach President of the supervisory board: Hans Kristian Langva Registry office: district court Cologne Register number: HRB 52 497 **************************************************************************** ------=_NextPartTM-000-e5c11ff1-4bb3-4471-9f08-8adebae2667b--