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Date: Wed, 19 Apr 2017 17:02:36 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] blockdev-mirror ,
 how to replace old nodename by new nodename ?
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To: Alexandre DERUMIER <aderumier@odiso.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

On Wed, 04/19 09:08, Alexandre DERUMIER wrote:
> Hi,
> 
> I'm trying to implement blockdev-mirror, to replace drive-mirror as we can pass more options with blockdev-mirror.
> 
> 
> I would like to mirror an attached blockdev to a new blockdev, then switch at the end of block-job-complete, like for drive-mirror.
> 
> 
> qemu command line (vm-138-disk-1.qcow2 filename on "drive-virtio0" nodename:
> 
> -blockdev {"node-name":"drive-virtio0","cache":{"direct":true},"driver":"qcow2","file":{"filename":"/var/lib/vz/images/138/vm-138-disk-1.qcow2","aio":"threads","driver":"file"}}
> -device virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,write-cache=on
> 
> 
> add a new blockdev with blockdev-add: (a file vm-138-disk-2.raw has been created before, I assign it to a "tempmirror" nodename)
> 
> 
> {"arguments":{"driver":"raw","cache":{"direct":true},"node-name":"tempmirror","file":{"driver":"file","aio":"threads","filename":"/var/lib/vz/images/138/vm-138-disk-2.raw"}},"execute":"blockdev-add"}
> 
> 
> blockdev-mirror:
> 
> {"arguments":{"job-id":"drive-virtio0","target":"tempmirror","sync":"full","replaces":"drive-virtio0","device":"drive-virtio0"},"execute":"blockdev-mirror"}
> 
> (I have try with or without replaces option)
> 
> then query-name-block-nodes, show vm-138-disk-2.raw file on tempmirror "node-name", and vm-138-disk1.qcow2 on "drive-virtio0" node-name
>  
> 
> I expected that both was switched, like for drive-mirror.

The replace/switch happens when you do block-job-complete.

And I think in your use case "replaces" is not needed. That one is for replacing
a node under quorum

Fam