[Xen-users] Xen 3.4 Qcow based Copy of write overlay for Centos base image does not work.

[Arun Sharma <arunain@xxxxxxxxx>]

Hello 

My requirement is to implement COW by having single base image and multiple vm having multiple cow files.

For this i have,  converted existing tap:aio supported base image of centos 5.2 and tested on xen. 
Since qcow2 based Centos52 works fine for me then i tried creating multiple cow files using qcow-create command.  But when i try to run the vm using cow file it does not work ? Any idea . 

Please see below steps which i did.

Assume that i have already working base image which works fine with tap:aio based driver.

1. Converted to qcow2 format.

    qemu-img-xen convert -O qcow2 CentosServer5.2_1.img CentosServer5.2_1_qcow2.img
     
    where  CentosServer5.2_1.img is converted to CentosServer5.2_1_qcow2.img


2.  Now creating vm with below xen config.  It worked.
 
         disk = [ 'tap:qcow2:/var/opt/espresso/centos/CentosServer5.2_1_qcow2.img,xvda,w',
         'tap:aio:/var/opt/espresso/centos/swap.img,xvdb,w'       ]

3. Now creating cow file based on above base image.

          qcow-create -f qcow2 100M centos.cow CentosServer5.2_1_qcow2.img

4. Trying to create vm now using below xen config.  Things fails here.

         disk = [ 'tap:qcow2:/var/opt/espresso/centos/centos.cow,xvda,w',
         'tap:aio:/var/opt/espresso/centos/swap.img,xvdb,w'     ]
  

        # xm create  centos.cfg 
           Using config file "./centos.cfg".
            Error: Device 51952 (tap) could not be connected. Setting up the backend failed. See the log files in /var/log/xen/ for details.


NOT SURE WHAT MISTAKE I AM DOING.



Xend logs are here.
-------------------------------

log/xen/ for details.
Traceback (most recent call last):
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 3602, in create_vbd
    dev_control.waitForDevice(devid)
  File "usr/lib64/python2.4/site-packages/xen/xend/server/DevController.py", line 164, in waitForDevice
    raise VmError("Device %s (%s) could not be connected. "
VmError: Device 51952 (tap) could not be connected. Setting up the backend failed. See the log files in /var/log/xen/ for details.
[2009-05-28 17:23:27 29552] ERROR (XendDomainInfo:476) VM start failed
Traceback (most recent call last):
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 456, in start
    XendTask.log_progress(31, 60, self._initDomain)
  File "usr/lib64/python2.4/site-packages/xen/xend/XendTask.py", line 209, in log_progress
    retval = func(*args, **kwds)
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2498, in _initDomain
    self._configureBootloader()
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2913, in _configureBootloader
    dom0._waitForDeviceUUID(dom0.create_vbd(vbd, disk))
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 3602, in create_vbd
    dev_control.waitForDevice(devid)
  File "usr/lib64/python2.4/site-packages/xen/xend/server/DevController.py", line 164, in waitForDevice
    raise VmError("Device %s (%s) could not be connected. "
VmError: Device 51952 (tap) could not be connected. Setting up the backend failed. See the log files in /var/log/xen/ for details.
[2009-05-28 17:23:27 29552] DEBUG (XendDomainInfo:2723) XendDomainInfo.destroy: domid=58
[2009-05-28 17:23:27 29552] DEBUG (XendDomainInfo:2203) No device model
[2009-05-28 17:23:27 29552] DEBUG (XendDomainInfo:2205) Releasing devices
[2009-05-28 17:23:27 29552] ERROR (XendDomainInfo:97) Domain construction failed
Traceback (most recent call last):
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 95, in create
    vm.start()
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 456, in start
    XendTask.log_progress(31, 60, self._initDomain)
  File "usr/lib64/python2.4/site-packages/xen/xend/XendTask.py", line 209, in log_progress
    retval = func(*args, **kwds)
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2498, in _initDomain
    self._configureBootloader()
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2913, in _configureBootloader
    dom0._waitForDeviceUUID(dom0.create_vbd(vbd, disk))
  File "usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 3602, in create_vbd
    dev_control.waitForDevice(devid)
  File "usr/lib64/python2.4/site-packages/xen/xend/server/DevController.py", line 164, in waitForDevice
    raise VmError("Device %s (%s) could not be connected. "
VmError: Device 51952 (tap) could not be connected. Setting up the backend failed. See the log files in /var/log/xen/ for details.




----------------------------

Any idea ?

Arun




 

        



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