Hello, Community!
With the popularity of virtual machines, more and more problems are occurring.
Today, I'd like to share with you a case of Failed to View All Disk Slots to Restore Windows VMs During Startup.
Problem Description
When I mount tools and reboot the system, it is not showing and the system login directs to windows.
It is informed that I cannot attach the OS DVD while the tool is mounted as you can see.
Problem Analysis
As tested in our lab. the result was as below :
1. For physical server, under-recovery mode, the server can discover two disks.
2. For the Hyper-V platform, under-recovery mode, the server can discover two disks.
3. For VMWare platform, under-recovery mode, server can discover two disks.
4. Only for the FC platform, there is only one disk to be found.
According to above situation, we checked in the dump XML file of that VM. found as below:
The disk letter of system disk is xvde. but the disk letter of the second disk is xvde . Due to FCV100R006C10 version uses the XEN virtualization platform, so the bus of disk and cdrom is IDE type. The IDE bus has a limitation that each of the two IDE controllers can connect to only two devices. It means that only four devices of IDE Device can be discovered in every VM without vmtools. It means that xvda/xvdb/xvdc/xvdd can be discovered.
You can see, the second disk was assigned xvde drive letter. xvde can not be discovered by VM without vmtools. When VM enters recovery mode, it does not use the PV driver which included by vmtools, it uses the common driver of windows, so the issue occurred.
This is determined by the product design. The product design is that the created VM must have a CD-ROM drive, and the drive letter is fixed to xvdb.
After we modify the dump XML file of this VM(modify drive letter of the second disk from xvde to xvdb), then we can discover the second disk under recovery mode
Root Cause
Due to the FC V100R006C10 version uses XEN virtualization platform, so the bus of disk and cdrom is IDE type. The IDE bus has a limitation that each of the two IDEcontrollers can connect to only two devices. It means that only four devices ofIDE Device can be discovered in every VM without vmtools. It means that xvda/xvdb/xvdc/xvdd can be discovered.
Solution
1. Remove all VMS except the VM which you need to recover to another host .
2. Login to the backend of this by gandalf , and switch to root.
3. Stop monitor service and vnad service on this host . and modify dump XML file of this VM. Restart monitor service and vnad service on this host. The commands are as follows:
4. Modify drive letter.
That's all for today. I hope it will be helpful to all of you!
If you have any other comments or want to know more, please leave a message below to let me know.
