On 03/25/2015 03:36 AM, Wen Congyang wrote: > Signed-off-by: Wen Congyang <we...@cn.fujitsu.com> > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > Signed-off-by: Yang Hongyang <yan...@cn.fujitsu.com> > Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com> > Signed-off-by: Gonglei <arei.gong...@huawei.com> > --- > 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 well-known) 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 s/checkpoint/checkpoints/ > +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(). s/dirver/driver/ > + > +== 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 s/transfered/transferred/ > + 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 s/when/on/ > + 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 == > +Primary: > + -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? > + > +Secondary: > + -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
signature.asc
Description: OpenPGP digital signature
