ToDo/Block/old

Material for next QEMU release

Coroutines in the block layer [Kevin]

• Programming model to simplify block drivers without blocking QEMU threads

Generic copy-on-read [Stefan]

• Populate image file to avoid fetching same block from backing file again later

Generic image streaming [Stefan]

• Make block_stream commands available for all image formats that support backing files

Live block copy

• Copy the contents of an image file while a guest is using it
• Mostly a libvirt feature based on QEMU's blockdev-snapshot-sync and block_stream

In-place qcow2 <-> qed conversion [Devin, GSoC 2011]:

• Fast conversion between qcow2 and qed image formats without copy all data
• Patches currently being reviewed and merged

VMDK enhancements [Fam, GSoC 2011]

• Implement latest VMDK specs to support modern image files
• Patches currently being reviewed and merged

Block I/O limits [Zhi Yong]

• Resource control for guest I/O bandwidth/iops consumption

Runtime WCE toggling [?]

• wce=none|on|off and run-time guest toggling support
• Prerequisite to switching away from cache=writethrough by default

Future changes

Cow overlay [Dong Xu "Robert"]

• Allow live block copy and image streaming to raw destination files

snapshot_blkdev and Backup API [Jes, Jagane]

• Support for consistent disk snapshots and dirty block tracking
• Allow backup software to integrate with QEMU

-blockdev [Markus?]

• Explicit user control over block device trees
• Perhaps base this on QEMU Object Model right away

QCOW3

• Extend qcow2 format to address current and future image format challenges
  • Feature bits for fine-grained file format extensions
  • Sub-clusters to reduce metadata size and fragmentation
  • Zero clusters for efficient sparse images and copy-on-read
  • luks-like key scheme that allows changing passphrase without re-encrypting data

iSCSI/NBD/Remote block device integration

• Enable remote access to disk images for live migration and other tasks
• Still unclear what will be done in this area

Pre/post block copy based on image streaming

• Working block migration that works with a separate migration thread

Avoid blocking QEMU threads

• Today loss of NFS connectivity can hang guests
• It's critical never to block the vcpu thread
• The iothread should also not block while the qemu mutex is held
• All blocking operations must be done asynchronously or in a worker thread

virtio-scsi [Paolo/Stefan]

• The next step after virtio-blk, full SCSI command set and appears as SCSI HBA in guest
• Real /dev/sda devices in guest
• No more modifying guest drivers to add simple storage protocol features

tcm_vhost [Stefan]

• Directly connect virtio-scsi with Linux in-kernel SCSI target
• Pass-through of host SCSI devices

qcow2 online resize [Zhi Yong]

• Handle snapshots
• Support shrinking

qed online resize [Zhi Yong]

• Support shrinking

Future changes

Cow overlay [Dong Xu "Robert"]

* Allow live block copy and image streaming to raw destination files

snapshot_blkdev and Backup API [Jes, Jagane]

* Support for consistent disk snapshots and dirty block tracking
* Allow backup software to integrate with QEMU

-blockdev [Markus?]

* Explicit user control over block device trees
* Perhaps base this on QEMU Object Model right away

QCOW3

* Extend qcow2 format to address current and future image format challenges
 * Feature bits for fine-grained file format extensions
 * Sub-clusters to reduce metadata size and fragmentation
 * Zero clusters for efficient sparse images and copy-on-read
 * luks-like key scheme that allows changing passphrase without re-encrypting data

iSCSI/NBD/Remote block device integration

* Enable remote access to disk images for live migration and other tasks
* Still unclear what will be done in this area

Pre/post block copy based on image streaming

* Working block migration that works with a separate migration thread

Avoid blocking QEMU threads

* Today loss of NFS connectivity can hang guests
* It's critical never to block the vcpu thread
* The iothread should also not block while the qemu mutex is held
* All blocking operations must be done asynchronously or in a worker thread

virtio-scsi [Paolo/Stefan]

* The next step after virtio-blk, full SCSI command set and appears as SCSI HBA in guest
* Real /dev/sda devices in guest
* No more modifying guest drivers to add simple storage protocol features

tcm_vhost [Stefan]

* Directly connect virtio-scsi with Linux in-kernel SCSI target
* Pass-through of host SCSI devices

qcow2 online resize [Zhi Yong]

* Handle snapshots
* Support shrinking

qed online resize [Zhi Yong]

* Support shrinking