Features/VirtioSCSI

Overview

A virtio storage interface for efficient I/O that overcomes virtio-blk limitations and supports advanced SCSI hardware.

Status

• Virtio device specification
  • Committed
  • http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.4.pdf
• Linux guest driver
  • Patch on mailing list
  • https://lkml.org/lkml/2012/2/5/75
• QEMU hardware emulation using SCSI emulation
  • Patches on mailing list
  • http://lists.gnu.org/archive/html/qemu-devel/2012-01/msg02012.html
• QEMU hardware emulation using vhost-scsi
  • (Stalled) work-in-progress, contact Stefan
  • http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/virtio-scsi
• Libvirt support
  • Patches on mailing list
  • http://www.redhat.com/archives/libvir-list/2012-January/msg00537.html

Future tasks

• Pick up vhost-scsi work again:
  • Port QEMU hw/virtio-scsi.c vhost-scsi support onto latest code; add QEMU Object Model (QOM) support
  • to the vhost-scsi device
  • Port LIO vhost-scsi code onto latest lio.git code and spec
  • Ensure vhost-scsi I/O still works
  • Design libvirt integration for LIO
• QEMU SCSI target:
  • Add support for WRITE SAME commands
  • Add support for rerror/werror to scsi-generic
• Complete virtio-scsi spec implementation:
  • Add support for hotplug events
  • Add support for asynchronous media change notifications

Features

• /dev/sda inside guest
• Multiple LUNs per PCI adapter, solves virtio-blk 1:1 scalability problem
• SCSI passthrough (tape, CD burning, ...)

Links

• KVM Forum 2011 presentation Virtio SCSI: An alternative virtualized storage stack for KVM