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

[Wen Congyang]

On 07/09/2015 09:55 AM, Dr. David Alan Gilbert wrote:
> * Wen Congyang (address@hidden) wrote:
>> On 07/08/2015 11:49 PM, Michael R. Hines wrote:
>>> 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.
>>
>> I have sent the v8. But the usage is not changed. You can setup the 
>> environment according to the wiki.
>> When we open nbd client, we need to connect to the nbd server. So I 
>> introduce a new command child_add to add NBD client
>> as a quorum child when the nbd server is ready.
>>
>> The nbd server is ready after you run the following command:
>> nbd_server_start 0:6262 # the secondary qemu will listen to host:port
>> nbd_server_add -w mc1   # the NBD server will know this disk is used as NBD 
>> server. The export name is its id wc1.
>>                         # -w means we allow to write to this disk.
>>
>> Then you can run the following command in the primary 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
>>
>> After this monitor command, nbd client has connected to the nbd server.
> 
> Ah! The 'child.file.export=mc1' wasn't there previously; I see Yang added 
> that to the wiki yesterday;
> that probably explains the problem that we've been having.

Sorry for this mistake.

Thanks
Wen Congyang

> 
> Dave
> 
>>
>> Thanks
>> Wen Congyang
>>
>>>
>>> - Michael
>>>
>>> .
>>>
>>
>>
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
> .
>