Features/VirtioSCSI
Overview
A virtio storage interface for efficient I/O that overcomes virtio-blk limitations and supports advanced SCSI hardware.
Features
- /dev/sda inside guest
- Multiple LUNs per PCI adapter, solves virtio-blk 1:1 scalability problem
- SCSI passthrough (tape, CD burning, ...)
Status
- Virtio device specification
- 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://www.spinics.net/lists/kvm/msg68444.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
- Update vhost-scsi to implement latest virtio-scsi device specification
- 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
- Use cases to flesh out:
- LUN hotplug
- CD-ROM/DVD burning passthrough
- Tape passthrough
- Multipath inside guest
- 100s of LUNs (scalability)
- Performance analysis
- Compare against virtio-blk I/O
- Compare against bare metal host SCSI
Links
- KVM Forum 2011 presentation Virtio SCSI: An alternative virtualized storage stack for KVM