Re: [Qemu-block] [Qemu-devel] [RFC PATCH COLO v2 00/13] Block replication for continuous checkpoints

[Michael R. Hines]

On 06/30/2015 11:11 PM, Wen Congyang wrote:
> On 07/01/2015 11:09 AM, Michael R. Hines wrote:
> > On 03/25/2015 04:36 AM, Wen Congyang wrote:
> > > Block replication is a very important feature which is used for
> > > continuous checkpoints(for example: COLO).
> > >
> > > Usage:
> > > Please refer to docs/block-replication.txt
> > >
> > > You can get the patch here:
> > > https://github.com/wencongyang/qemu-colo/commits/block-replication-v2
> > >
> > > Changs Log:
> > > V2:
> > > 1. Redesign the secondary qemu(use image-fleecing)
> > > 2. Use Error objects to return error message
> > > 3. Address the comments from Max Reitz and Eric Blake
> > >
> > > Wen Congyang (13):
> > >     docs: block replication's description
> > >     quorum: allow ignoring child errors
> > >     NBD client: connect to nbd server later
> > >     Add new block driver interfaces to control block replication
> > >     quorum: implement block driver interfaces for block replication
> > >     NBD client: implement block driver interfaces for block replication
> > >     allow writing to the backing file
> > >     Allow creating backup jobs when opening BDS
> > >     block: Parse "backing_reference" option to reference existing BDS
> > >     Backup: clear all bitmap when doing block checkpoint
> > >     qcow2: support colo
> > >     skip nbd_target when starting block replication
> > >     Don't allow a disk use backing reference target
> > >
> > >    block.c                    | 242 +++++++++++++++++++++++-
> > >    block/Makefile.objs        |   2 +-
> > >    block/backup.c             |  12 ++
> > >    block/nbd.c                | 171 +++++++++++++++--
> > >    block/qcow2.c              | 447 
> > > ++++++++++++++++++++++++++++++++++++++++++++-
> > >    block/qcow2.h              |   6 +
> > >    block/quorum.c             | 143 ++++++++++++++-
> > >    docs/block-replication.txt | 147 +++++++++++++++
> > >    include/block/block.h      |   5 +
> > >    include/block/block_int.h  |  13 ++
> > >    include/qemu/hbitmap.h     |   8 +
> > >    qapi/block.json            |  16 ++
> > >    tests/qemu-iotests/051     |  13 ++
> > >    tests/qemu-iotests/051.out |  13 ++
> > >    util/hbitmap.c             |  19 ++
> > >    15 files changed, 1230 insertions(+), 27 deletions(-)
> > >    create mode 100644 docs/block-replication.txt
> > When I try this patch with the MicroCheckpointing codebase, I'm having trouble 
> > starting up the secondary/backup VM
> > using the branch "block-replication-v7"
> >
> > $ qemu-system-x86_64 -drive if=none,driver=raw,file=file.raw,id=nbd_target1 
> > -drive 
> > if=virtio,driver=replication,mode=secondary,export=foo,file.file.filename=active_disk.qcow2,file.driver=qcow2,file.backing_reference.drive_id=nbd_target1,file.backing_reference.hidden-disk.file.filename=hidden_disk.qcow2,file.backing_reference.hidden-disk.driver=qcow2,file.backing_reference.hidden-disk.allow-write-backing-file=on
> >
> > Block format 'qcow2' used by device '' doesn't support the option 
> > 'backing_reference.hidden-disk.allow-write-backing-file'
> >
> > What am I doing wrong here?
> The command is wrong. If you use the branch block-replication-v7, the command 
> line should like:
> -drive 
> if=none,driver=raw,file=/data/images/kvm/suse/suse11_3.img,id=colo1,cache=none,aio=native
>  -drive 
> if=virtio,driver=replication,mode=secondary,throttling.bps-total-max=70000000,file.file.filename=/mnt/ramfs/active_disk.img,file.driver=qcow2,file.backing.file.filename=/mnt/ramfs/hidden_disk.img,file.backing.driver=qcow2,file.backing.allow-write-backing-file=on,file.backing.backing.backing_reference=colo1
>
> Thanks
> Wen Congyang
>
> > - Michael
> >
> > .

Can you also tell me what's wrong with the primary/source VM command 
line? Or could you update the documentation please?
Am I using the correct branch?

Here's my command line:

qemu-system-x86_64: -drive 
if=virtio,driver=quorum,read-pattern=fifo,no-connect=on,children.0.file.filename=/kvm_repo/image.raw,children.0.driver=raw,children.1.file.driver=nbd,children.1.file.host=192.168.168.3,children.1.file.port=6262,children.1.file.export=foo,children.1.driver=replication,children.1.mode=primary,children.1.ignore-errors=on: 

Failed to read export length

What exactly is the purpose of the "export" parameter?

Thanks,

- Michael