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Re: [Qemu-devel] [Qemu-block] [RFC PATCH COLO v2 01/13] docs: block repl
Re: [Qemu-devel] [Qemu-block] [RFC PATCH COLO v2 01/13] docs: block replication's description
Wed, 25 Mar 2015 09:38:55 -0600
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
On 03/25/2015 03:36 AM, Wen Congyang wrote:
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Yang Hongyang <address@hidden>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Gonglei <address@hidden>
> docs/block-replication.txt | 147
> 1 file changed, 147 insertions(+)
> create mode 100644 docs/block-replication.txt
Grammar review only (I'll leave the technical review to others)
> diff --git a/docs/block-replication.txt b/docs/block-replication.txt
> new file mode 100644
> index 0000000..874ed8e
> --- /dev/null
> +++ b/docs/block-replication.txt
> @@ -0,0 +1,147 @@
> +Block replication
> +Copyright Fujitsu, Corp. 2015
> +Copyright (c) 2015 Intel Corporation
> +Copyright (c) 2015 HUAWEI TECHNOLOGIES CO.,LTD.
Space after comma in English writing.
> +This work is licensed under the terms of the GNU GPL, version 2 or later.
> +See the COPYING file in the top-level directory.
> +The block replication is used for continuous checkpoints. It is designed
Sounds better as either of:
The block replication feature is...
Block replication is...
> +for COLO that Secondary VM is running. It can also be applied for FT/HA
Please define COLO and FT/HA on first use (okay to abbreviate elsewhere
in the document, but the first use should not assume the acronym is
s/for COLO that/for COLO (COurse-grain LOck-stepping), where the/
> +scene that Secondary VM is not running.
s/for FT/HA scene that/for the FT/HA (Fault-tolerance/High Assurance)
scenario, where the/
> +This document gives an overview of block replication's design.
> +== Background ==
> +High availability solutions such as micro checkpoint and COLO will do
> +consecutive checkpoint. The VM state of Primary VM and Secondary VM is
> +identical right after a VM checkpoint, but becomes different as the VM
> +4) The hidden-disk is created automatically. It buffers the original content
> +that is modified by the primary VM. It should also be an empty disk, and
> +the dirver supports bdrv_make_empty().
> +== New block driver interface ==
> +We add three block driver interfaces to control block replication:
> +a. bdrv_start_replication()
> + Start block replication, called in migration/checkpoint thread.
> + We must call bdrv_start_replication() in secondary QEMU before
> + calling bdrv_start_replication() in primary QEMU.
> +b. bdrv_do_checkpoint()
> + This interface is called after all VM state is transfered to
> + Secondary QEMU. The Disk buffer will be dropped in this interface.
> + The caller must hold the I/O mutex lock if it is in migration/checkpoint
> + thread.
> +c. bdrv_stop_replication()
> + It is called when failover. We will flush the Disk buffer into
> + Secondary Disk and stop block replication. The vm should be stopped
> + before calling it. The caller must hold the I/O mutex lock if it is
> + in migration/checkpoint thread.
> +== Usage ==
> + -drive if=xxx,driver=quorum,read-pattern=fifo,\
> + children.0.file.filename=1.raw,\
> + children.0.driver=raw,\
> + children.1.file.driver=nbd+colo,\
> + children.1.file.host=xxx,\
> + children.1.file.port=xxx,\
> + children.1.file.export=xxx,\
> + children.1.driver=raw,\
> + children.1.ignore-errors=on
This command line looks like multiple arguments because of the leading
whitespace on succeeding lines. I don't know if there is any better way
to format it, though, to make it obvious that it is all a single
argument to -drive.
> + Note:
> + 1. NBD Client should not be the first child of quorum.
> + 2. There should be only one NBD Client.
> + 3. host is the secondary physical machine's hostname or IP
> + 4. Each disk must have its own export name.
Maybe a note 5 to call out the formatting aspect of the command line?
> + -drive if=none,driver=raw,file=1.raw,id=nbd_target1 \
> + -drive if=xxx,driver=qcow2+colo,file=active_disk.qcow2,export=xxx,\
> + backing_reference.drive_id=nbd_target1,\
> + backing_reference.hidden-disk.file.filename=hidden_disk.qcow2,\
> + backing_reference.hidden-disk.driver=qcow2,\
> + backing_reference.hidden-disk.allow-write-backing-file=on
> + Then run qmp command:
> + nbd_server_start host:port
> + Note:
> + 1. The export name for the same disk must be the same in primary
> + and secondary QEMU command line
> + 2. The qmp command nbd_server_start must be run before running the
> + qmp command migrate on primary QEMU
> + 3. Don't use nbd_server_start's other options
> + 4. Active disk, hidden disk and nbd target's length should be the
> + same.
> + 5. It is better to put active disk and hidden disk in ramdisk.
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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Re: [Qemu-devel] [RFC PATCH COLO v2 01/13] docs: block replication's description, Fam Zheng, 2015/03/26
[Qemu-devel] [RFC PATCH COLO v2 02/13] quorum: allow ignoring child errors, Wen Congyang, 2015/03/25
[Qemu-devel] [RFC PATCH COLO v2 03/13] NBD client: connect to nbd server later, Wen Congyang, 2015/03/25