Features/VirtioSCSI

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Revision as of 15:04, 20 February 2012 by Stefanha (talk | contribs)

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

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
    • Multi-queue (with fine-grained locking in the Linux driver?)
  • Use cases to test:
    • CD-ROM/DVD burning passthrough
    • Tape passthrough
    • 100s of LUNs (scalability)
  • Use cases to flesh out:
    • LUN hotplug (known to work with manual hotplug)
    • Multipath inside guest
  • Performance analysis
    • Compare against virtio-blk I/O (rough numbers: 6% slower on iozone with a tmpfs-backed disk)
    • Compare passthrough performance against bare metal host SCSI
    • Measure scalability and where the bottlenecks are (full virtqueues? locks?)

Specifications

Repositories

* QEMU (virtio-scsi): git://github.com/bonzini/qemu.git virtio-scsi
* Linux (virtio-scsi): git://github.com/bonzini/virtio-scsi.git
* QEMU (vhost-scsi): http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/virtio-scsi
* tcm_vhost: https://github.com/stefanha/linux/tree/tcm_vhost

Links

Retrieved from "https://wiki.qemu.org/index.php?title=Features/VirtioSCSI&oldid=2765"