Hello, coming from the "low cost NFS storage thread" I will open a new one about a topic that might be interesting for others too.
We see a quite a heavy latency penalty using KVM VirtIO disks in comparison to ESX. Doing one I/O onto disk inside a VM usually adds 370us of overhead in the virtualisation layer. This has been tested with VirtIO-SCSI and windows guest (2K3). More here (still now answer yet): http://lists.nongnu.org/archive/html/qemu-discuss/2013-12/msg00028.html A comparison for small sequential 1K I/Os on a NFS datastore in our setup gives: - access NFS inside the hypervisor - 12.000 I/Os per second - or 83us latency - access DISK inside ESX VM that resides on NFS - 8000 I/Os per second - or 125us latency - access DISK inside OVirt VM that resides on NFS - 2200 I/Os per second - or 450us latency Even the official document at http://www.linux-kvm.org/page/Virtio/Block/Latency suggest that the several mechanisms (iothread/vcpu) at least have a overhead of more than 200us Has anyone experienced something simlar. If these latency are normal it would make no sense to think about SSDs inside a central storage (be it ISCSI or NFS or whatever). Markus
**************************************************************************** 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. Ãber 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 ****************************************************************************
_______________________________________________ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users