Re: [Qemu-devel] [PATCH COLO-BLOCK v7 00/17] Block replication for continuous checkpoints

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 07/07/2015 08:38 PM, Wen Congyang wrote:
> On 07/08/2015 12:56 AM, Michael R. Hines wrote:
>> On 07/07/2015 04:23 AM, Paolo Bonzini wrote:
>>> On 07/07/2015 11:13, Dr. David Alan Gilbert wrote:
>>>>>> This log is very stange. The NBD client connects to NBD server, and NBD server wants to read data
>>>>>> from NBD client, but reading fails. It seems that the connection is closed unexpectedly. Can you
>>>>>> give me more log and how do you use it?
>>>> That was the same failure I was getting.   I think it's that the NBD server and client are in different
>>>> modes, with one of them expecting the export.
>>> nbd_server_add always expects the export.
>>>
>>> Paolo
>>>
>> OK, Wen, so your wiki finally does reflect this, but now we're back to the "export not found error".
>>
>> Again, here's the exact command line:
>>
>> 1. First on the secondary VM:
>>
>> qemu-system-x86_64 .........snip...........  -drive if=none,driver=qcow2,file=foo.qcow2,id=mc1,cache=none,aio=native -drive if=virtio,driver=replication,mode=secondary,throttling.bps-total-max=70000000,file.file.filename=active_disk.qcow2,file.driver=qcow2,file.backing.file.filename=hidden_disk.qcow2,file.backing.driver=qcow2,file.backing.allow-write-backing-file=on,file.backing.backing.backing_reference=mc1
>>
>> 2. Then, then HMP commands:
>>
>> nbd_server_start 0:6262
>> nbd_server_add -w mc1
>>
>> 3. Then the primary VM:
>>
>> qemu-system-x86_64 .........snip...........  -drive if=virtio,driver=quorum,read-pattern=fifo,no-connect=on,children.0.file.filename=bar.qcow2,children.0.driver=qcow2,children.1.file.driver=nbd,children.1.file.host=127.0.0.1,children.1.file.port=6262,children.1.driver=replication,children.1.mode=primary,children.1.ignore-errors=on
>>
>> With the error: Server requires an export name
>>
>> *but*, your wiki has no export name on the primary VM size, so I added the export name back which is on your old wiki:
>>
>> qemu-system-x86_64 .........snip...........  -drive if=virtio,driver=quorum,read-pattern=fifo,no-connect=on,children.0.file.filename=bar.qcow2,children.0.driver=qcow2,children.1.file.driver=nbd,children.1.file.export=mc1,children.1.file.host=127.0.0.1,children.1.file.port=6262,children.1.driver=replication,children.1.mode=primary,children.1.ignore-errors=on: Failed to read export length
>>
> Hmm, I think you use v7 version. Is it right?
> In this version, the correct useage for primary qemu is:
> 1. qemu-system-x86_64 .........snip...........  -drive if=virtio,driver=quorum,read-pattern=fifo,id=disk1,
>                        children.0.file.filename=bar.qcow2,children.0.driver=qcow2,
>
> Then run hmp monitor command(It should be run after you run nbd_server_add in the secondary qemu):
> child_add disk1 child.driver=replication,child.mode=primary,child.file.host=127.0.0.1,child.file.port=6262,child.file.export=mc1,child.file.driver=nbd,child.ignore-errors=on
>
> Thanks
> Wen Congyang
>
>> And server now says:
>>
>> nbd.c:nbd_handle_export_name():L416: export not found
>> nbd.c:nbd_send_negotiate():L562: option negotiation failed
>>
>> .
>>
>

OK, I'm totally confused at this point. =)

Maybe it would be easier to just wait for your next clean patchset + 
documentation which is all consistent with each other.

- Michael